fix(auth-core): Improve auth-core quality

[gtema]

• Implement AuthTokenScope::matches() for wildcard cache lookup (None
  matches any value)
• Update get_scope_auth/find_scope_authz to iterate with matches()
  instead of HashMap::get
• Remove custom Serialize for Project/Domain; remove skip_serializing_if
  for postcard compat
• Rename AuthResponse::token field type from AuthToken to TokenInfo
• Change OpenStackAuthType::auth trait signature to take &HashMap
  (borrow instead of owned)
• Rename AuthToken::set_header return type from Result<&'a mut
  HeaderMap> to Result<()>
• Improve from_reqwest_response error handling for non-JSON and identity
  API errors
• Update httpmock JSON expectations to include explicit null fields
• Fix AuthError variants: box AuthReceiptResponse, wrap AuthTokenError
  in Auth::AuthToken
• Fix federation and websso callback server test race conditions with
  oneshot channels
• Add 18 AuthTokenScope::matches() tests and 9 state cache tests
• Reorder struct fields alphabetically per project standards