Remove unused agi code

[juggernot325]

Description

This PR removes some database function (and the corresponding mock functions) that are no longer used across the code base for tidiness.

I also updated the CreateAssetGroupSelector API client function to use a PUT instead of a POST as the latter has been deprecated. While fixing this I noticed that the response body didn't match the struct we were trying to parse into, so I updated that to match as well.

Motivation and Context

• Clean code is happy code

How Has This Been Tested?

• Existing tests still pass

Types of changes

• Chore (a change that does not modify the application functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Documentation updates are needed, and have been made accordingly.
• I have added and/or updated tests to cover my changes.
• All new and existing tests passed.
• My changes include a database migration.

[mistahj67]

LGTM
Thanks for cleaning these up! 🧹 🧼