site-kit-wp: Error message in wp admin does not contain plugin name.

Bug Description

Today I ran into this message in my admin screen:

Unknown Error (code: Invalid JSON response). To fix this, redo the plugin setup.

Please include which plugin name in the error message, because the only way I could figure out that this was related to Site Kit was to view the source.

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

• All notices added to non-Site Kit screens should clearly identify as originating from the Site Kit plugin by prefixing the message with the plugin name
  E.g.

  Site Kit by Google: Unknown Error (code: Invalid JSON response). To fix this, redo the plugin setup.

Implementation Brief

• Update all notices in the Authentication and Idea_Hub classes to have Site Kit by Google: prefix before the content of the notice: https://github.com/google/site-kit-wp/blob/14e8604318a29a7dfc928029f992c2ad8a6df60c/includes/Core/Authentication/Authentication.php#L1051-L1053 https://github.com/google/site-kit-wp/blob/14e8604318a29a7dfc928029f992c2ad8a6df60c/includes/Core/Authentication/Authentication.php#L1101-L1103 https://github.com/google/site-kit-wp/blob/14e8604318a29a7dfc928029f992c2ad8a6df60c/includes/Core/Authentication/Authentication.php#L1154-L1156 https://github.com/google/site-kit-wp/blob/14e8604318a29a7dfc928029f992c2ad8a6df60c/includes/Modules/Idea_Hub.php#L310-L312 https://github.com/google/site-kit-wp/blob/14e8604318a29a7dfc928029f992c2ad8a6df60c/includes/Modules/Idea_Hub.php#L346-L348 (If possible this should be localized.)

Test Coverage

• N/A

QA Brief

• QAing this would require checking all notices from Site Kit that are displayed in non Site Kit pages of the WordPress Dashboard.
• The following notices can be checked:
  • URL mismatch notice: Try changing the Site URL and Home URL of the installation (I changed from http to https) and see a notice show up.
  • Authentication notice: From your Google account, revoke Site Kit’s access to your Google account. This should make Site Kit show an authentication error (this sometimes require clearing the local and session storage).
  • OAuth error: While setting up Site Kit, cancel instead of continuing to give Site Kit access to Google account. This will trigger a setup interruption error.
  • Idea Hub notices: Set up Idea Hub (enable ideaHubModule feature flag from Tester Settings) and see notices from Idea Hub in your WordPress Dashboard.

Changelog entry

• Update admin notice messages to have Site Kit by Google: prefixes.