Add Job Name Validation Check

[atjones0011]

Azkaban requires all job names to be unique within a project. The current behavior when there's a naming collision is for Azkaban to throw a 500 error that doesn't provide useful details to the deploying user about what went wrong. This leads to a lot of confusion for developers who are encountering the issue for the first time.

Instead of the current behavior, I propose a pre-deploy check for uniqueness among job names in a project. This provides the benefit of being able to provide a more detailed error message that will allow developers to resolve their naming collision more quickly.

[mtth]

Apologies for the delayed response. There's already a duplicate job name check; can you elaborate on when it's not sufficient?

[atjones0011]

I'm no longer working on this project and don't recall exactly why the duplicate job name check wasn't working. @Ralnoc might be able to provide more details here.