T5: OAuth and the client API over HTTP

96 integration tests through PrivaPubHost, the real pipeline end to end:
- OAuth: the token's subject is the persona, and neither the token response,
  verify_credentials nor the stored token entries name the root. A wrong password shows
  an error and sets no login cookie; a login without the antiforgery token is a 400; the
  return address never leaves the site; deny answers access_denied with no code; another
  root's persona re-renders the choice with no code; a banned root is sent back to the
  login and a code issued before the ban buys no token; force_login asks again; a code
  works once and its reuse revokes the token it bought; password and refresh_token
  grants are refused; a client_credentials token gets 401 on user routes; a read-only
  token gets 403 with a Mastodon error on POST /api/v1/statuses; follow covers
  read:follows; revoke works; the login and authorize pages send their CSP and no-store;
  the 11th /oauth/login from one address in a minute is a 429.
- Accounts: sign-up, duplicates in any case, invalid models answer 400 with a message,
  login and logout, recovery email, settings, password change, invitation sign-up and
  login (refusing a persona named after the login), recovery without an email, through
  an unreachable mail server, with a wrong and with a valid code, token refresh, the 11th
  sign-up from one address, expired, garbage and foreign-key JWTs.
- Personas: a rootId in the body is ignored, the username regex and reserved names hold,
  personas and groups share ReservedName, an update delivers Update{Person} to followers,
  PublishedOn and the id's day fall within two weeks before creation, the list holds only
  one's own personas, another root's persona cannot be updated.
- Groups: communities and circles are created, joining takes the code and the password,
  members leave and owners cannot, a remote follow request becomes a member only on
  approval, a circle never shows in lookup, account by id, v2 search or /@name, and its
  /flock and /wardens answer 404 unsigned and to non-members, 200 to a member's signed GET.
- Moderation (Exclusive, it suspends localhost): ban, unban and remove; non-admins get
  403; reports are listed without the reporter and resolved; domain blocks are inserted,
  listed and deleted, bad domains refused, and a suspended server's delivery is answered
  202 and kept nowhere; the data endpoints.
- AdminCommands: exit codes 0, 1 and 2 and the resulting policies.

Fixed:
- A banned or removed root kept using /clientapi with its JWT until it expired: only /api
  re-checked the root. JwtEvents.TokenValidated now loads the root and fails the request
  when it is banned or deleted, and takes the policy claims from the database, so a
  demoted admin loses admin at once (and a promoted one gains it).
- The 401 and 403 bodies JwtEvents writes were PascalCase while every other /clientapi
  answer is camelCase; they now use the web defaults.
- /clientapi/user/sniff/again (token refresh) answered an empty 200; it now answers a
  fresh JwtUser, like login.
- Password recovery answered SMTP reply codes as HTTP statuses (421, 454, 554, and 550 for
  an invalid address); a mail server failure is now 503 and an invalid address 400.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Services/RootUsersService.cs

@@ -411,13 +411,13 @@ namespace PrivaPub.Services
 						if (!smtpClient.IsConnected)
 						{
 							Logger.LogError($"Failed to connect to the SMTP server({AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpServer}).");
-							return result.Invalidate(Localizer["Failed to send email."], (int)SmtpStatusCode.ServiceNotAvailable);
+							return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable);
 						}
 					}
 					catch (Exception ex)
 					{
 						Logger.LogError(ex, $"Error at connection to the SMTP server({AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpServer}).");
-						return result.Invalidate(Localizer["Failed to send email."], (int)SmtpStatusCode.ServiceNotAvailable, exception: ex);
+						return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable, exception: ex);
 					}
 
 					try
@@ -427,21 +427,21 @@ namespace PrivaPub.Services
 						{
 							Logger.LogError($"Failed SMTP authentication of {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
 							return result.Invalidate(Localizer["Failed to send email."],
-								(int)SmtpStatusCode.TemporaryAuthenticationFailure);
+								StatusCodes.Status503ServiceUnavailable);
 						}
 					}
 					catch (Exception ex)
 					{
 						Logger.LogError(ex, $"Failed SMTP authentication of {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
 						return result.Invalidate(Localizer["Failed to send email."],
-							(int)SmtpStatusCode.TemporaryAuthenticationFailure, exception: ex);
+							StatusCodes.Status503ServiceUnavailable, exception: ex);
 					}
 
 					try
 					{
 						var toParsed = await smtpClient.VerifyAsync(user.Email);
 						if (toParsed == null)
-							return result.Invalidate(Localizer["Invalid email."], (int)SmtpStatusCode.MailboxUnavailable);
+							return result.Invalidate(Localizer["Invalid email."], StatusCodes.Status400BadRequest);
 					}
 					catch (OperationCanceledException ex)
 					{
@@ -483,7 +483,7 @@ Eugene from collAnon, following is the password recovery link:
 					catch (Exception ex)
 					{
 						Logger.LogError(ex, $"Error at email sending to {user.Email} from {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
-						return result.Invalidate(Localizer["Failed to send email."], (int)SmtpStatusCode.TransactionFailed, exception: ex);
+						return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable, exception: ex);
 					}
 
 					await smtpClient.DisconnectAsync(quit: true);