Implement Project entity

[ivlevdenis]

https://github.com/toggl/toggl_api_docs/blob/master/chapters/projects.md

[nifadyev]

According to migration guide, Projects related endpoints are moved into /me and /workspace/<id>/ paths. So related logic and entity structure should be refactored.

[nifadyev]

Rough plan:

• Necessary endpoints (available on free plan):

• GET /me/projects Implement essential Project logic #58
• GET /me/projects/paginated Add Project fetching, creation, update and deletion #74
• GET/POST/PATCH {workspace_id}/projects Add Project fetching, creation, update and deletion #74
• GET/PUT/DELETE {workspace_id}/projects/{project_id} Add Project fetching, creation, update and deletion #74
• Implement Project bulk editing #77

• Cover new logic with tests and type annotations