Add POSIX Regex support for PostgreSQL and MySQL

[larsschwegmann]

This PR adds support for the Postgres "~" posix regex operator and the MySQL "RLIKE" operator as a filter operator for char fields ("__posix_regex").

Description

I needed support for filtering with the "~" operator offered by postgres (9.7.3. POSIX Regular Expressions)

Motivation and Context

The POSIX regex operator is more powerful than the LIKE statement.

How Has This Been Tested?

I added two tests for the postgres and mysql backends

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[abondar]

Hi!

Can you please rebase on new develop, previous commit had faulty version of mssql there, so CI was failing

[larsschwegmann]

Hi @abondar , I just rebased onto the latest develop 😄

[abondar]

@larsschwegmann there seems to be mypy issues in CI

You can run mypy locally with make lint

[larsschwegmann]

@abondar Thanks, I have run that locally and fixed the mypy issue now 👍

[coveralls]

Pull Request Test Coverage Report for Build 11092126846

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

• 10 of 13 (76.92%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 88.991%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tortoise/backends/mysql/executor.py	2	3	66.67%
tortoise/contrib/postgres/regex.py	5	6	83.33%
tortoise/filters.py	1	2	50.0%

Totals
Change from base Build 11067278859:	-0.02%
Covered Lines:	5973
Relevant Lines:	6597

---

💛 - Coveralls