feat: Add MongoCache

[Skelmis]

Description

Adds in a MongoCache backend

I know this branch is called Feature/timeouts, I pushed to the wrong one by mistake.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Integration tests.

Checklist:

• I have added in logging for all relevant areas
• I have performed a self-review of my own code
• My code follows the style guidelines of this project
• New and existing unit tests pass locally with my changes
• I have made corresponding changes to the documentation
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works

[coveralls]

Pull Request Test Coverage Report for Build 1802390832

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 105 of 230 (45.65%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-6.8%) to 84.505%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
antispam/caches/mongo/mongo_cache.py	28	79	35.44%
antispam/caches/mongo/document.py	58	132	43.94%

Totals
Change from base Build 1798547649:	-6.8%
Covered Lines:	1363
Relevant Lines:	1609

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💛 - Coveralls