Adding tag community, database and REST API endpoints

[drew2a]

This PR contains core-side logic for #6214

Design decisions behind the Community:

• Tag operations gossiped transitively across the network
• Pull-based gossip is used
• For tags' integrity check ipv8 signatures are used
• The simplified algorithm is: "Request 10 tags from a random peer every 5 seconds"

Design decisions behind the DB:

• We will use a separate database: https://github.com/drew2a/tribler/blob/feature/tag_community/src/tribler-core/tribler_core/components/tag/db/tag_db.py
• We will store not only tags but also user operations on tags (only one operation per one user):

       class TorrentTagOp(db.Entity):
            id = orm.PrimaryKey(int, auto=True)

            torrent_tag = orm.Required(lambda: TorrentTag)
            peer = orm.Required(lambda: Peer)

            operation = orm.Required(int)
            time = orm.Required(int)
            signature = orm.Required(bytes)
            updated_at = orm.Required(datetime.datetime, default=datetime.datetime.utcnow)

            orm.composite_key(torrent_tag, peer)

• We will use two counters to access information about added and removed tags without aggregation:

        class TorrentTag(db.Entity):
            ...
            added_count = orm.Required(int, default=0)
            removed_count = orm.Required(int, default=0)

• We will use an indicator to distinguish local user operations and remote user operations:

        class TorrentTag(db.Entity):
            ...
            local_operation = orm.Optional(int) 

[devos50]

Please note: I will add more tests in the next PR. This PR should be merged to main to let @devos50 work on the GUI part.

Feel free to add these tests in this PR, I can just rebase my branch when you make changes (adding tests to this PR should not merge conflict with my work). 👍

[devos50]

@drew2a I notice that there are a few uncovered lines which could probably be covered with a carefully designed test (e.g., in the TagCommunity class). Were you planning on adding additional tests in this PR?

Also, I think the remaining pylint errors can be fixed 👍

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[devos50]

A test on Windows 64-bit is failing:

def test_calculate_category_invalid_announce_list():
        torrent_info = {b"info": {b"name": b"term1", b"length": 1234},
                        b"announce-list": [[]], b"comment": b"lorem ipsum"}
>       assert default_category_filter.calculateCategory(torrent_info, "my torrent") == "xxx"
E       AssertionError: assert 'other' == 'xxx'
E         - xxx
E         + other

src\tribler-core\tribler_core\components\metadata_store\category_filter\tests\test_category.py:33: AssertionError

That's unexpected since this test looks deterministic. Let's see if this persists.

[devos50]

retest this please