[FEATURE] Integrate gitlab code into stable client codebase

[prasadtalasila]

Describe the feature

As a developer I want to integrate gitlab codebase into stable codebase So That the code quality gets improved.

Describe the problems your feature request solves

The preview codebase uses gitlab as backend for fulfilling features on library and digital twins preview pages. This code does not yet follow SOLID principles and has some code quality issues.
As a first step the core gitlab interface needs to be brought out into the stable codebase.

Describe the solution you'd like

The following code needs to be brought out into stable codebase.

Filename	Desirable location
Asset.ts	src/model/definitions/asset.ts Imported into and re-exported in src/model/api.ts
preview util	src/model/backend/gitlab
constants in preview	src/model/backend/gitlab/constants.ts
store	Move the required redux slices to src/model/backend/gitlab/store

Describe alternatives you've considered

Ideally, I would like to limit the work to the following files.

1. gitlab.ts
2. DigitalTwin.ts
3. DigitalTwinUtils.ts
4. Constants

But that would require serious splitting of existing preview code. If there is a way to accomplish the task of refactoring the above four files, that would be preferable.

Success Criterion

Checklist:

• Existing preview features remains intact
• Code and tests are successfully migrated
• Code is refactored as per SOLID principles
• Test coverage remains the same
• Codeclimate issues are resolved