[#719] Apple 네이티브 인증을 유지하고 프로필 책임을 서버로 이전한다

Application/Infra/Sources/Service/FunctionAPIClient.swift

@@ -124,6 +124,7 @@ struct FirebaseCustomTokenResponse: Decodable {
 struct AppleCustomTokenRequest: Encodable {
     let challengeId: String
     let authorizationCode: String
+    let displayName: String?
 }
 
 struct AppleAccountLinkRequest: Encodable {

Application/Infra/Sources/Service/SocialLogin/AppleAuthenticationServiceImpl.swift

@@ -42,38 +42,18 @@ final class AppleAuthenticationServiceImpl: AuthenticationService {
             let response = try await authenticateWithAppleAsync(
                 hashedNonce: challenge.hashedNonce
             )
-
+
+            let displayName = response.fullName?.displayName
+
             logger.debug("Requesting custom token from Firebase Function")
             let customToken = try await requestAppleCustomToken(
                 challengeId: challenge.challengeId,
-                authorizationCode: response.authorizationCode
+                authorizationCode: response.authorizationCode,
+                displayName: displayName
             )
-            
+
             logger.debug("Signing in with custom token")
             let result = try await Auth.auth().signIn(withCustomToken: customToken)
-
-            let changeRequest = result.user.createProfileChangeRequest()
-            var displayName: String?
-
-            if let fullName = response.fullName {
-                let formatter = PersonNameComponentsFormatter()
-                formatter.style = .long
-                let formattedName = formatter.string(from: fullName)
-                if !formattedName.isEmpty {
-                    displayName = formattedName
-                }
-            }
-
-            if displayName == nil {
-                let doc = try await store
-                    .document(FirestorePath.userData(result.user.uid, document: .info))
-                    .getDocument()
-                displayName = doc.data()?["appleName"] as? String
-            }
-
-            changeRequest.displayName = displayName ?? ""
-            changeRequest.photoURL = nil //  Apple ID 프로필 사진 URL은 제공되지 않음
-            try await changeRequest.commitChanges()
 
             logger.info("Successfully signed in with Apple")
             return result.user.makeResponse(providerID: .apple)
@@ -224,13 +204,15 @@ final class AppleAuthenticationServiceImpl: AuthenticationService {
 
     private func requestAppleCustomToken(
         challengeId: String,
-        authorizationCode: String
+        authorizationCode: String,
+        displayName: String?
     ) async throws -> String {
         let response = try await FunctionAPIClient.shared.send(
             .requestAppleCustomToken,
             payload: AppleCustomTokenRequest(
                 challengeId: challengeId,
-                authorizationCode: authorizationCode
+                authorizationCode: authorizationCode,
+                displayName: displayName
             ),
             requiresAuthentication: false
         )
@@ -239,6 +221,15 @@ final class AppleAuthenticationServiceImpl: AuthenticationService {
     }
 }
 
+extension PersonNameComponents {
+    var displayName: String? {
+        let formatter = PersonNameComponentsFormatter()
+        formatter.style = .long
+        let name = formatter.string(from: self)
+        return name.isEmpty ? nil : name
+    }
+}
+
 private extension AppleAuthenticationServiceImpl {
     func mapAppleAPIError(_ error: Error) -> Error {
         if let emailError = error.apiEmailError {

Application/Infra/Tests/Service/FunctionAPIEndpointTests.swift

@@ -52,16 +52,47 @@ struct FunctionAPIEndpointTests {
         #expect(endpoint.path == "/auth/apple/access-token")
     }
 
-    @Test("Apple custom token 요청은 challenge와 authorization code만 인코딩한다")
-    func Apple_custom_token_요청은_challenge와_authorization_code만_인코딩한다() throws {
+    @Test("Apple custom token 요청은 display name을 포함할 수 있다")
+    func Apple_custom_token_요청은_display_name을_포함할_수_있다() throws {
         let request = AppleCustomTokenRequest(
             challengeId: "challenge-id",
-            authorizationCode: "authorization-code"
+            authorizationCode: "authorization-code",
+            displayName: "Apple User"
+        )
+
+        #expect(
+            try encodedKeys(request) == [
+                "challengeId",
+                "authorizationCode",
+                "displayName"
+            ]
+        )
+    }
+
+    @Test("Apple custom token 요청은 없는 display name을 인코딩하지 않는다")
+    func Apple_custom_token_요청은_없는_display_name을_인코딩하지_않는다() throws {
+        let request = AppleCustomTokenRequest(
+            challengeId: "challenge-id",
+            authorizationCode: "authorization-code",
+            displayName: nil
         )
 
         #expect(try encodedKeys(request) == ["challengeId", "authorizationCode"])
     }
 
+    @Test("Apple 이름은 custom token 요청용 display name으로 변환한다")
+    func Apple_이름은_custom_token_요청용_display_name으로_변환한다() {
+        var fullName = PersonNameComponents()
+        fullName.givenName = "Apple"
+
+        #expect(fullName.displayName == "Apple")
+    }
+
+    @Test("비어 있는 Apple 이름은 display name으로 변환하지 않는다")
+    func 비어_있는_Apple_이름은_display_name으로_변환하지_않는다() {
+        #expect(PersonNameComponents().displayName == nil)
+    }
+
     @Test("Apple 계정 연결 요청은 credential email을 포함할 수 있다")
     func Apple_계정_연결_요청은_credential_email을_포함할_수_있다() throws {
         let request = AppleAccountLinkRequest(