[PM-20592] [PM-22737] [PM-22738] Send grant validator (#6151)

**feat**: create `SendGrantValidator` and initial `SendPasswordValidator` for Send access grants  
**feat**: add feature flag to toggle Send grant validation logic  
**feat**: add Send client to Identity and update `ApiClient` to generic `Client`  
**feat**: register Send services in DI pipeline  
**feat**: add claims management support to `ProfileService`  
**feat**: distinguish between invalid grant and invalid request in `SendAccessGrantValidator`

**fix**: update parsing of `send_id` from request  
**fix**: add early return when feature flag is disabled  
**fix**: rename and organize Send access scope and grant type  
**fix**: dotnet format

**test**: add unit and integration tests for `SendGrantValidator`  
**test**: update OpenID configuration and API resource claims

**doc**: move documentation to interfaces and update inline comments  

**chore**: add TODO for future support of `CustomGrantTypes`

src/Core/KeyManagement/KeyManagementServiceCollectionExtensions.cs

@@ -9,6 +9,7 @@ public static class KeyManagementServiceCollectionExtensions
     public static void AddKeyManagementServices(this IServiceCollection services)
     {
         services.AddKeyManagementCommands();
+        services.AddSendPasswordServices();
     }
 
     private static void AddKeyManagementCommands(this IServiceCollection services)

src/Core/KeyManagement/Sends/ISendPasswordHasher.cs

@@ -9,7 +9,6 @@ public interface ISendPasswordHasher
     /// <param name="sendPasswordHash">The send password that is hashed by the server.</param>
     /// <param name="clientPasswordHash">The user provided password hash that has not yet been hashed by the server for comparison.</param>
     /// <returns>true if hashes match false otherwise</returns>
-    /// <exception cref="InvalidOperationException">Thrown if the server password hash or client password hash is null or empty.</exception>
     bool PasswordHashMatches(string sendPasswordHash, string clientPasswordHash);
 
     /// <summary>