allow tags to be writeable via the addon api

[eviljeff]

part of mozilla/addons#8516 - addon tags should be writeable. The tags are only allowed from a pre-selected list (how to expose that list via the API?), and limited to how many can be selected per addon.

[ioanarusiczki]

@eviljeff

On AMO dev:

• using the addon endpoint, tag information can be sent at creation An example: {"categories": {"firefox": ["general"]}, "version": {"upload": "3297f89108664056941524ca5692c8c3", "license": 18}, "compatibility": ["firefox", "android"], "tags": ["scholar", "download", "reddit", "chat", "dark mode", "facebook", "duckduckgo"], "summary": {"en-US":"a test for themes"}}

• tags can be modified with a PATCH request {"tags": ["scholar", "download", "reddit", "chat", "dark mode", "vpn"]}

• more than 10 tags are not permitted -> "Ensure this field has no more than 10 elements.", something not defined as tag (not part of the admin tag list) is a 404 not found.

These are all expected.

• an empty array sent with a PATCH request has a delete role {"tags": []} -> can't tell if it's expected but I guess it should be allowed.

I've noticed 2 things:

• same tag can be sent 10 times -> maybe using it twice should throw an error such as "duplicate tag" {"tags": ["scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar"]}

• I get the 201 Created on versions endpoint with a JSON where I add tags {"upload": "fd7dd5921fed461e8cf1dd0e3b501856", "license":18,"compatibility": ["firefox"], "tags": ["privacy", "pixiv"]} and also a 200 response when I send a PATCH request such as {"tags": ["privacy", "pixiv"]} on https://addons-dev.allizom.org/api/v5/addons/addon/621000/versions/1693315/ I think this should throw some error instead, adding tags has no effect when creating new version or making changes on a specific version.

Let me know if I should file issues for these 2.

[eviljeff]

I've noticed 2 things:

* same tag can be sent 10 times -> maybe using it twice should throw an error such as "duplicate tag"
  `{"tags": ["scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar", "scholar"]}`

it's a weird input but duplicates are harmless - unless it's actually adding the same tag 10 times(!) (I don't think that's even possible at the database level)

* I get the 201 Created  on versions endpoint with a JSON where I add tags `{"upload": "fd7dd5921fed461e8cf1dd0e3b501856", "license":18,"compatibility": ["firefox"], "tags": ["privacy", "pixiv"]}` and also a 200 response when I send a PATCH request such as
  `{"tags": ["privacy", "pixiv"]}` on https://addons-dev.allizom.org/api/v5/addons/addon/621000/versions/1693315/
  I think this should throw some error instead, adding tags has no effect when creating new version or making changes on a specific version.

REST apis just ignore extra json keys and tags isn't a property for the version api so that's fine.