Ensure cronjob names are unique

[seanhamlin]

At present, it is possible to define 2 cronjobs in .lagoon.yml with the same name.

      - name: test-cronjobs
        schedule: "M * * * *"
        command: /app/console do:stuff
        service: cli
      - name: test-cronjobs
        schedule: "M * * * *"
        command: /app/console do:something:different
        service: cli

Only the last one will 'win', and only a single cronjob will be made. This is confusing for the end user.

Proposed solution

Either pass the build with warnings, or fail the build entirely. Either way, we should inform the use that they need to adjust their .lagoon.yml file.

[shreddedbacon]

I think failure would be better, as long as the failure can happen early