Allow introducing job and run termination reasons without breaking compatibility

[jvstme]

Problem

To avoid breaking backward compatibility with clients, introducing any new job or run termination reason is delayed until the next minor release. This results in less informative termination reasons, such as INTERRUPTED_BY_NO_CAPACITY instead of INSTANCE_UNREACHABLE, and causes inconveniences when adding new features.

Solution

A possible solution is to switch from enum variants to strings for termination reason fields.

Workaround

No response

Would you like to help us implement this feature by sending a PR?

Yes