feat: POST /user/contacts — save a contact to the device addressbook

[FlavioPulli]

WhatsApp syncs the contact list across devices via app state (the same channel as mute/pin/archive), and whatsmeow already applies incoming contact mutations back into Store.Contacts. The API exposes only the read side (GET /user/contacts); this adds the write side.

POST /user/contacts {phone, fullName, firstName?} builds a contact-index mutation on the critical_unblock_low patch carrying a ContactAction (FullName/FirstName + SaveOnPrimaryAddressbook: true, which asks the primary phone to also store the contact in the system addressbook) and sends it through the official Client.SendAppState primitive. After the resync SendAppState triggers, the saved contact shows up in GET /user/contacts like any contact saved on the phone itself.

Verified end to end on a paired Android device (contact appears in the phone's WhatsApp list and system addressbook); in our production since 2026-07-22.

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Retargeted to develop (replaces #129), as requested by @iagocotta in #128 (comment).

Note that main and develop have no common ancestor — the GitHub API refuses to compare them (No common ancestor between main and develop) — so the base branch of the original PR could not simply be edited. This branch was created from develop and the commit cherry-picked onto it.

The import paths were changed from evolution-foundation/evolution-go to EvolutionAPI/evolution-go, which is the module path develop still declares in its go.mod. No other change.

Verified on this branch: go build ./... and go vet ./... both pass.

Summary by Sourcery

Add support for saving WhatsApp contacts to the device address book via a new POST /user/contacts endpoint wired through the user handler and service.

New Features:

• Introduce POST /user/contacts API to create or update a contact in the WhatsApp contact list and device address book.

Enhancements:

• Extend user handler and service interfaces with a SaveContact operation backed by whatsmeow app state mutations for contact syncing.

[sourcery-ai]

Reviewer's Guide

Adds a POST /user/contacts endpoint that builds and sends a WhatsApp app-state contact mutation so the primary device saves a contact into both WhatsApp’s contact list and the system address book, wiring it through routes, handler, and service layers with basic validation and logging.

Sequence diagram for POST /user/contacts saving a contact via WhatsApp app state

sequenceDiagram
  actor User
  participant GinRouter
  participant UserHandler
  participant UserService
  participant WhatsAppClient

  User->>GinRouter: POST /user/contacts
  GinRouter->>UserHandler: SaveContact(ctx)
  UserHandler->>UserHandler: ctx.MustGet(instance)
  UserHandler->>UserHandler: ctx.ShouldBindBodyWithJSON(data)
  UserHandler->>UserService: SaveContact(data, instance)
  UserService->>UserService: ensureClientConnected(instance.Id)
  UserService->>WhatsAppClient: SendAppState(context.Background(), patch)
  alt SendAppState error
    WhatsAppClient-->>UserService: error
    UserService->>UserService: LogError(instance.Id, jid.String(), err)
    UserService-->>UserHandler: error
    UserHandler-->>User: 500 Internal Server Error
  else SendAppState success
    WhatsAppClient-->>UserService: ok
    UserService->>UserService: LogInfo(instance.Id, fullName, jid.String())
    UserService-->>UserHandler: nil
    UserHandler-->>User: 200 {message: success}
  end

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File-Level Changes

Change	Details	Files
Introduce service-layer operation to create and send a WhatsApp app-state contact mutation that saves a contact to the device addressbook.	Define SaveContactStruct DTO with phone, fullName, and optional firstName fields mapped to JSON. Implement userService.SaveContact to validate inputs, derive firstName when omitted, construct JID and appstate.PatchInfo for the critical_unblock_low contact index, and send it via Client.SendAppState. Add contactMutationVersion constant and use waSyncAction.ContactAction fields (FullName, FirstName, SaveOnPrimaryAddressbook) to drive the mutation. Integrate logging for success and error paths when sending app-state patches.	pkg/user/service/save_contact.go pkg/user/service/user_service.go
Add HTTP handler and routing for POST /user/contacts that forwards validated payloads to the service method and exposes the new endpoint in the API.	Extend UserHandler interface with SaveContact method and wire it in the router under /user/contacts POST. Implement user_handler.SaveContact to fetch the instance from context, bind JSON body into SaveContactStruct, perform basic field-length validation, call UserService.SaveContact, and return appropriate HTTP responses. Annotate the handler with Swagger/OpenAPI-style comments including summary, description, tags, params, and response types.	pkg/routes/routes.go pkg/user/handler/user_handler.go pkg/user/handler/save_contact.go

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• In the HTTP handler, you bind into a *SaveContactStruct using ctx.ShouldBindBodyWithJSON(&data), which results in a pointer-to-pointer; consider binding into a value (var data user_service.SaveContactStruct and pass &data) to align with Gin’s binding expectations.
• The handler performs its own phone/fullName presence check while the service also validates and returns the same error; you could centralize this validation in the service layer to avoid duplication and keep error behavior in one place.
• In SaveContact, you use context.Background() for SendAppState; passing ctx.Request.Context() from the HTTP handler would let the operation be cancelled if the client disconnects or the request times out.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In the HTTP handler, you bind into a `*SaveContactStruct` using `ctx.ShouldBindBodyWithJSON(&data)`, which results in a pointer-to-pointer; consider binding into a value (`var data user_service.SaveContactStruct` and pass `&data`) to align with Gin’s binding expectations.
- The handler performs its own `phone`/`fullName` presence check while the service also validates and returns the same error; you could centralize this validation in the service layer to avoid duplication and keep error behavior in one place.
- In `SaveContact`, you use `context.Background()` for `SendAppState`; passing `ctx.Request.Context()` from the HTTP handler would let the operation be cancelled if the client disconnects or the request times out.

## Individual Comments

### Comment 1
<location path="pkg/user/handler/save_contact.go" line_range="35-36" />
<code_context>
+		return
+	}
+
+	var data *user_service.SaveContactStruct
+	err := ctx.ShouldBindBodyWithJSON(&data)
+	if err != nil {
+		ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
</code_context>
<issue_to_address>
**issue (bug_risk):** Binding into a pointer-to-pointer is likely incorrect and may prevent proper JSON deserialization.

`data` is declared as `*user_service.SaveContactStruct`, so `&data` is `**user_service.SaveContactStruct`, which Gin’s binders don’t expect and may break deserialization. Use a concrete value instead:

```go
var data user_service.SaveContactStruct
if err := ctx.ShouldBindBodyWithJSON(&data); err != nil {
    ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
    return
}
// pass &data to the service
```
</issue_to_address>

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[sourcery-ai]

issue (bug_risk): Binding into a pointer-to-pointer is likely incorrect and may prevent proper JSON deserialization.

data is declared as *user_service.SaveContactStruct, so &data is **user_service.SaveContactStruct, which Gin’s binders don’t expect and may break deserialization. Use a concrete value instead:

var data user_service.SaveContactStruct
if err := ctx.ShouldBindBodyWithJSON(&data); err != nil {
    ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
    return
}
// pass &data to the service