Config-UI: Delete single connection endpoint

[kevin-kline]

Description

We need a way to delete connections for Plugins.

Describe the solution you'd like

• We need a button in the "Connections" tables for each plugin, on connection items. (Frontend)
• We need a backend route to delete the connection information. (Backend)

Has the Feature been Requested Before?

No.

Additional context

PLEASE NOTE: Only Jira currently supports multi-sources in the DB. So the Jira plugin can delete source from the database. GitLab and Jenkins will need to simply assign their credentials in the .env file to empty.

[klesh]

Make sure pop up a Confirmation dialog