Move WordPressComRestApiErrorDomain to APIInterface

This DRYs the definition, makes the constant available to both
Objective-C and Swift, and removes the need for custom builder and
checker.

See @crazytonyli's suggestion from
wordpress-mobile/WordPressKit-iOS#782 (comment)

Author: mokagio

WooCommerce/WordPressAuthenticator/WordPressKit/APIInterface/include/WordPressComRestApiErrorDomain.h

@@ -0,0 +1,9 @@
+#import <Foundation/Foundation.h>
+
+/// Error domain of `NSError` instances that are converted from `WordPressComRestApiEndpointError`
+/// and `WordPressAPIError<WordPressComRestApiEndpointError>` instances.
+///
+/// This matches the compiler generated value and is used to ensure consistent error domain across error types and SPM or Framework build modes.
+///
+/// See `extension WordPressComRestApiEndpointError: CustomNSError` in CoreAPI package for context.
+static NSString *const _Nonnull WordPressComRestApiErrorDomain = @"WordPressKit.WordPressComRestApiError";

WooCommerce/WordPressAuthenticator/WordPressKit/CoreAPI/WordPressAPIError+NSErrorBridge.swift

@@ -1,4 +1,7 @@
 import Foundation
+#if SWIFT_PACKAGE
+import APIInterface
+#endif
 
 /// Custom `NSError` bridge implementation.
 ///
@@ -86,8 +89,7 @@ extension WordPressAPIError: CustomNSError {
 /// And in cases where additional user info was provided, they need to be carried over to the `NSError` instances.
 extension WordPressComRestApiEndpointError: CustomNSError {
 
-    // This value is the same as the `WordPressComRestApiErrorDomain` constant generated by Swift compiler.
-    public static let errorDomain = "WordPressKit.WordPressComRestApiError"
+    public static let errorDomain = WordPressComRestApiErrorDomain
 
     public var errorCode: Int {
         code.rawValue

WooCommerce/WordPressAuthenticator/WordPressKit/CoreAPI/WordPressComRestApiErrorDomain.swift

@@ -244,8 +244,9 @@ - (NSError *)processMediaUploadErrors:(NSArray *)errorList {
             errorMessage = errorInfo[@"message"];
         }
         NSDictionary *errorDictionary = @{NSLocalizedDescriptionKey: errorMessage};
-        error = [NSError wordPressComRestApiErrorWithCode:WordPressComRestApiErrorCodeUploadFailed
-                                                 userInfo:errorDictionary];
+        error = [[NSError alloc] initWithDomain:WordPressComRestApiErrorDomain
+                                           code:WordPressComRestApiErrorCodeUploadFailed
+                                       userInfo:errorDictionary];
     }
     return error;
 }
@@ -297,8 +298,9 @@ - (void)deleteMedia:(RemoteMedia *)media
                                    }
                                } else {
                                    if (failure) {
-                                       NSError *error = [NSError wordPressComRestApiErrorWithCode:WordPressComRestApiErrorCodeUnknown
-                                                                                         userInfo:nil];
+                                       NSError *error = [[NSError alloc] initWithDomain:WordPressComRestApiErrorDomain
+                                                                                   code:WordPressComRestApiErrorCodeUnknown
+                                                                               userInfo:nil];
                                        failure(error);
                                    }
                                }
@@ -369,8 +371,9 @@ -(void)getVideoPressToken:(NSString *)videoPressID
                                    }
                                } else {
                                    if (failure) {
-                                       NSError *error = [NSError wordPressComRestApiErrorWithCode:WordPressComRestApiErrorCodeUnknown
-                                                                                         userInfo:nil];
+                                       NSError *error = [[NSError alloc] initWithDomain:WordPressComRestApiErrorDomain
+                                                                                   code:WordPressComRestApiErrorCodeUnknown
+                                                                               userInfo:nil];
                                        failure(error);
                                    }
                                }

WooCommerce/WordPressAuthenticator/WordPressKit/Services/MediaServiceRemoteREST.m

@@ -179,9 +179,9 @@ - (void)createWPComBlogWithUrl:(NSString *)blogUrl
             NSMutableDictionary *userInfo = [[NSMutableDictionary alloc] init];
             userInfo[WordPressComRestApi.ErrorKeyErrorMessage] = localizedErrorMessage;
             userInfo[NSLocalizedDescriptionKey] = localizedErrorMessage;
-            NSError *errorWithLocalizedMessage = [NSError wordPressComRestApiErrorWithCode:WordPressComRestApiErrorCodeUnknown
-                                                                                  userInfo:userInfo];
-
+            NSError *errorWithLocalizedMessage = [[NSError alloc] initWithDomain:WordPressComRestApiErrorDomain
+                                                                            code:WordPressComRestApiErrorCodeUnknown
+                                                                        userInfo:userInfo];
             failure(errorWithLocalizedMessage);
         } else {
             success(responseObject);
@@ -228,7 +228,7 @@ - (void)createWPComBlogWithUrl:(NSString *)blogUrl
 
 - (NSError *)errorWithLocalizedMessage:(NSError *)error {
     NSError *errorWithLocalizedMessage = error;
-    if ([error hasWordPressComRestApiErrorDomain] &&
+    if ([error.domain isEqual:WordPressComRestApiErrorDomain] &&
         [error.userInfo objectForKey:WordPressComRestApi.ErrorKeyErrorCode] != nil) {
 
         NSString *localizedErrorMessage = [self errorMessageForError:error];