[Tagging] Enforce limit on number of tags per object

[bradenmacdonald]

Description

"As a system administrator, I want to limit the maximum number of tags that can be applied to any one object, to ensure smooth functioning of the tagging system."

Details

Update the tagging API so that there is a maximum limit of 100 tags that can be applied to any one object (e.g. per XBlock).

Ensure there is an automated test in place to verify that this limit is enforced.

Notes

Thanks to this limit:

• any APIs which return the tags of an individual object only do not need pagination. We can remove pagination from any such APIs during this ticket, to simplify them.
• any bug which results in "runaway" creation of tags (e.g. through a bug in auto-tagging) won't cause major problems.
• performance of the tagging API will be more consistent and less prone to huge spikes as it would if any one object had thousands of tags