Rails: Support agentk applier errors

Issue: #417730 (closed)

What does this MR do and why?

• Background issue: #397001 (closed)
• Technical design: #416989 (closed)
• Adds support for receiving error details in request in the reconciliation API
• Adds spec to verify the changes
• The request validation spec has also been updated to verify the termination_progress that may be received as a sibling field

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