API v2 paginated tasks

[c8y3]

Implement endpoint GET /api/v2/cases/{case_identifier}/tasks to get a paginated list of tasks:

• successful GET should return 200
• field data should be present
• fields data should be [] when there is no tasks
• field total should return 1 when there is a task
• it should accept page, per_page, order_by and sort_dir parameters
• fields last_page, current_page and next_page should be present in result
• check returned object is uniform with other endpoints
• deprecate GET /case/tasks/list
• openapi document GET /api/v2/cases/{case_identifier}/tasks
• openapi deprecate GET /case/tasks/list

[c8y3]

Some tasks to do:

• use object PaginationParameter and factor code for Cases and Iocs
• introduce a method at the business level rather than going directly to the database
• factor this line (or variants) everywhere order_func = desc if pagination_parameters.get_direction() == 'desc' else asc
• check the return values of the task, use the correct schema object
• factor construction of paginated result with other similar endpoints