Support multi-tenant

[kerthcet]

What would you like to be added:

Right now, we use the project_id for multi-tenant case, but in realty, what we hope to achieve is like in a single team, we have several team members, from the dashboard, we can know how many experiments each of them ran, and how many money they spent individually.

To support this, we need to think out a way to support multi-tenant.

Why is this needed:

Completion requirements:

This feature requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[kerthcet]

/milestone v0.2.0

[kerthcet]

I think we have two ways:

• Use the project_id as the minimum unit for isolation, then what we can do for our users is like: for every api key, they can create a project id, and they organize different projects from their side, like an organization. Every user launch the dashboard they can only see their experiments. The pros is we don't need to have our own user tables in the db. The cons is every user can only see their dashboards, if they want to see the organization experiments, it's not possible from alphatrion side.
• We have our own users then when init the project, it would like ìnit(project_id = <>, user_id = <>`. We have the whole RBAC system in our system, it's a bit complex but support the multi-tenant out-of-the-box.