Fix tag duplication issue (#37)

- fix tag duplication
- test tag deduplication at document level
- prep work for next release in README.md

Author: tib

README.md

@@ -3,9 +3,9 @@
 The FeatherOpenAPI library makes it easy to define OpenAPI specifications using Swift in a type-safe way.
 
 [
-    ![Release: 1.0.0-beta.2](https://img.shields.io/badge/Release-1%2E0%2E0--beta%2E2-F05138)
+    ![Release: 1.0.0-beta.3](https://img.shields.io/badge/Release-1%2E0%2E0--beta%2E3-F05138)
 ](
-    https://github.com/feather-framework/feather-openapi/releases/tag/1.0.0-beta.2
+    https://github.com/feather-framework/feather-openapi/releases/tag/1.0.0-beta.3
 )
 
 ## Features
@@ -34,7 +34,7 @@ The FeatherOpenAPI library makes it easy to define OpenAPI specifications using
 Use Swift Package Manager; add the dependency to your `Package.swift` file:
 
 ```swift
-.package(url: "https://github.com/feather-framework/feather-openapi", exact: "1.0.0-beta.2"),
+.package(url: "https://github.com/feather-framework/feather-openapi", exact: "1.0.0-beta.3"),
 ```
 
 Then add `FeatherOpenAPI` to your target dependencies:

Sources/FeatherOpenAPI/Document/DocumentRepresentable.swift

@@ -38,7 +38,18 @@ extension DocumentRepresentable {
 
     /// Collects all tags referenced by the document.
     public var referencedTags: [OpenAPITagRepresentable] {
-        paths.values.map { $0.referencedTags }.flatMap { $0 }
+        var seen = Set<String>()
+        return paths.values
+            .map { $0.referencedTags }
+            .flatMap { $0 }
+            .filter { tag in
+                let name = tag.openAPITag().name
+                if seen.contains(name) {
+                    return false
+                }
+                seen.insert(name)
+                return true
+            }
     }
 
     /// Collects all security requirements referenced by the document.