Rails: Handle devfile gem validation errors as UI errors instead of 500 exceptions

• MR (Rails): Properly handle Devfile::CliError (!127289 - merged)
• Issue (devfile-gem): Devfile Gem: Handle devfile gem validation erro... (#419477 - closed)
• MR (devfile-gem): https://gitlab.com/gitlab-org/remote-development/devfile-gem/-/merge_requests/42+
• Likely duplicate issues:
  • #409069 (closed)

Description

As a user, I want devfile validation errors to be presented as a descriptive user error and not a 500 error.

This should addresses several "User initiated errors" from the epic: Robust Error Handling and Logging (&10461 - closed)

Acceptance Criteria

• The 500 errors described in &10461 (closed) should now be returned as error messages in the Web UI.
• We should also handle any errors from the #get_all call in the reconcile logic as well, as discussed here: !126785 (comment 1496417083)
  • Any failures in parsing/flattening a single workspace should not prevent other workspaces from being processed

Technical Requirements

• Adds a custom Devfile::CliError exception to the devfile gem. MR: https://gitlab.com/gitlab-org/remote-development/devfile-gem/-/merge_requests/42+
• Rescues that exception in Rails and handles it as a domain error, which should automatically get routed back to the UI as a GraphQL error. MR: Pending