adding pipeline server

[sherl0cks]

What does this PR do?

• Adds pipeline_server_url to Engagement.
• Removes the test section from the pull request template due to the nature of this repo.
• Reorders the definitions for easier viewing in swagger editor

Is there a relevant Issue open for this?

No -

Are there any other relevant resources that should be reviewed as well?

Who would you like to review this?

/cc @oybed

[sherl0cks]

Closing this PR per convo with @oybed to leave this out for now