Add black formatting

[RobbeSneyders]

Fixes #1498

I've added the changes as 2 separate commits for easy review:

• Add the configuration changes to run black as part of pre-commit
• Run black formatting

If you have a big PR in progress I can rerun the formatting after merging @Ruwann.

[coveralls]

Pull Request Test Coverage Report for Build 2562062579

• 501 of 527 (95.07%) changed or added relevant lines in 36 files are covered.
• 13 unchanged lines in 8 files lost coverage.
• Overall coverage remained the same at 94.707%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
connexion/decorators/decorator.py	1	2	50.0%
connexion/exceptions.py	9	10	90.0%
connexion/jsonifier.py	2	3	66.67%
connexion/options.py	13	14	92.86%
connexion/resolver.py	21	22	95.45%
connexion/apis/abstract.py	27	30	90.0%
connexion/spec.py	32	36	88.89%
connexion/security/security_handler_factory.py	31	36	86.11%
connexion/middleware/security.py	24	33	72.73%

Files with Coverage Reduction	New Missed Lines	%
connexion/decorators/decorator.py	1	55.56%
connexion/decorators/response.py	1	89.09%
connexion/exceptions.py	1	95.12%
connexion/json_schema.py	1	85.11%
connexion/middleware/abstract.py	1	85.71%
connexion/options.py	1	77.42%
connexion/security/security_handler_factory.py	1	83.61%
connexion/middleware/security.py	6	83.66%

Totals
Change from base Build 2562047116:	0.0%
Covered Lines:	2702
Relevant Lines:	2853

---

💛 - Coveralls

[Ruwann]

Thanks!

Currently working on the big serialization/validation middleware PR, so would indeed be nice to wait after that one