Multi-data connections support for Gitlab

[Startrekzky]

Description

An EE user Qianxin wants to import data from multiple Gitlab repos as the user has multiple keys and EE cannot support it for now.
@leglars suggested using Dev Lake instead of EE to achieve this goal in the future.

Describe the solution you'd like

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Has the Feature been Requested Before?

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Describe alternatives you've considered

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[klesh]

We can start working on it due to #455 has been finalized

[warren830]

Plan of Attack

1. update gitlab/api/connection to load and save through db not .env
2. update all entities with new field connection_id
3. update all tasks

[klesh]

I think the most important part, is to update every single Tool Layer Entities to include this very basic field...
And refactor all converter, to include "connectionId" as part of is id
Check JIRA implementation, you will see... it's very, very, huge change...

[klesh]

I think the most important part, is to update every single Tool Layer Entities to include this very basic field... And refactor all converter, to include "connectionId" as part of is id Check JIRA implementation, you will see... it's very, very, huge change...

My bad. you mentioned this part.

[warren830]

closed by #2260