Define db models in Golang

[easyCZ]

In order to interact with the database from our Golang based usage component, we need to define Gorm models for the database objects.

Define models for the following tables:

• Workspace
• Workspace Instance
• Team

Additional ones will be added as needed.

PRs:

• [usage] Configure DB credentials and connect #10295
• [usage] Establish database connection #10218
• [usage] Define db.Workspace model #10293
• [usage] Add db.WorkspaceInstance model in golang #10367
• [usage] Add db.Project model in golang #10368
• [usage] Add db.Team model in golang #10369