Properly display the error message upon container expiration policy validation

Summary

Follow up of !34063 (comment 357968187)

With !34063 (merged), regex used within container expiration policies are now validated.

If a user submits an invalid regex, an alert toast will be displayed with Something went wrong while updating (see examples !34063 (merged)).

This is quite vague. The rest API actually answers a very precise error. Example for regex [:

{
  "message": {
    "container_expiration_policy.name_regex_keep": [
      "not valid RE2 syntax: missing ]: ["
    ]
  }
}

The frontend can infer which field is wrong and why.

Improvements

  • Have a better and more precise error message

Risks

  • The error message is not displayed at all

Optional: Intended side effects