Remove association between ChatName and Integration - Step 3: drop chat_names.integration_id

This issue is part of the epic &9418 (closed). See that epic for more details.

About

We want to remove the association between a ChatName and an Integration in order to be able to identify users in Slack without a project or integration.

In previous issues, we made the association between ChatName and Integration optional in database modelling #384963 (closed) and in the codebase #384973 (closed).

In this step, we will drop the database chat_names.integration_id column later.

Milestone

This must be done in a milestone following the one that #384973 (closed) was released in, as we should only drop this column when the application is not longer using it.

Proposal

• Drop chat_names.integration_id column.
• For some views like app/views/profiles/chat_names/_chat_name.html.haml they will need to be modified to no longer display integration/project information (this is fine!).

Availability & Testing

We have Slack e2e tests in review, but they are not yet working in the pipeline.

Please ping @sgregory2 to run the tests when the changes are available in staging-ref.