Feature/announce api cog

[VottonDev]

Summary

PR for https://github.com/KoalaBotUK/KoalaBotFrontend/issues/437 that adds API routes for announce cog.

Checklist

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)

• Have you tested the changes? (pytest & dpytest)
• Have you followed PEP-8 for naming and styling?
• Has your code been properly documented with RestructuredText docstrings?
• Have you added your changes to CHANGELOG.md under the [Unreleased] heading?
• If your code added new bot commands, have you updated documentation.json?

• All of this code is your own, or follows the author repo's licence.

[lgtm-com]

This pull request introduces 6 alerts when merging 7dadc18 into 6e9ebdb - view on LGTM.com

new alerts:

• 5 for Unused import
• 1 for Module imports itself

[codecov]

Codecov Report

Merging #332 (6611177) into master (8713ece) will increase coverage by 0.02%.
The diff coverage is 91.22%.

❗ Current head 6611177 differs from pull request most recent head 5e9b48b. Consider uploading reports for the commit 5e9b48b to get more accurate results

@@            Coverage Diff             @@
##           master     #332      +/-   ##
==========================================
+ Coverage   86.52%   86.54%   +0.02%     
==========================================
  Files         111      114       +3     
  Lines        8095     8146      +51     
==========================================
+ Hits         7004     7050      +46     
- Misses       1091     1096       +5     

Flag	Coverage Δ
unittests	86.54% <91.22%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
koala/cogs/announce/db.py	100.00% <ø> (ø)
tests/cogs/base/test_core.py	98.64% <ø> (-0.01%)	⬇️
tests/cogs/announce/test_api.py	71.42% <71.42%> (ø)
koala/cogs/announce/api.py	96.00% <96.00%> (ø)
koala/cogs/announce/__init__.py	100.00% <100.00%> (ø)
koala/cogs/announce/cog.py	97.14% <100.00%> (ø)
koala/cogs/announce/models.py	91.66% <100.00%> (ø)
tests/cogs/announce/conftest.py	100.00% <100.00%> (ø)

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[lgtm-com]

This pull request introduces 3 alerts when merging 0d2ef60 into 8713ece - view on LGTM.com

new alerts:

• 3 for Unused import

[lgtm-com]

This pull request introduces 3 alerts when merging 2bb83c6 into 8713ece - view on LGTM.com

new alerts:

• 3 for Unused import

[lgtm-com]

This pull request introduces 3 alerts when merging 6611177 into 8713ece - view on LGTM.com

new alerts:

• 3 for Unused import

[lgtm-com]

This pull request introduces 3 alerts when merging 5e9b48b into 8713ece - view on LGTM.com

new alerts:

• 3 for Unused import