api: Create access-control API for signing keys

[gioelecerati]

What does this pull request do? Explain your changes. (required)

Creates a set of API for signing keys, as first milestone toward access control

Specific updates (required)

• Create signing key schema
• POST create up to 10 signing keys, retrieving the private key if the keypair only on creation
• GET retrieve a list of your existing signing keys, with only the public key
• DELETE a signing key
• UPDATE a signing key, disabling it
• Create a EC P-256 keypair in pem format for JWT generations
• Tests

How did you test each of these updates (required)

yarn test - postman

Does this pull request close any open issues?

Fixes #1284

Screenshots (optional):

Checklist:

• I have read the CONTRIBUTING document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

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Name	Status	Preview	Updated
livepeer-studio	✅ Ready (Inspect)	Visit Preview	Sep 22, 2022 at 10:01PM (UTC)

[codecov]

Codecov Report

Merging #1275 (63f7781) into master (25b49e4) will increase coverage by 0.30400%.
The diff coverage is 62.88660%.

@@                 Coverage Diff                 @@
##              master       #1275         +/-   ##
===================================================
+ Coverage   51.06138%   51.36538%   +0.30400%     
===================================================
  Files             66          68          +2     
  Lines           4334        4431         +97     
  Branches         786         805         +19     
===================================================
+ Hits            2213        2276         +63     
- Misses          1842        1865         +23     
- Partials         279         290         +11     

Impacted Files	Coverage Δ
packages/api/src/controllers/signing-key.ts	60.67416% <60.67416%> (ø)
packages/api/src/test-helpers.ts	80.85106% <66.66667%> (-0.46762%)	⬇️
packages/api/src/controllers/access-control.ts	100.00000% <100.00000%> (ø)
packages/api/src/store/db.ts	82.22222% <100.00000%> (+0.19974%)	⬆️
packages/api/src/controllers/helpers.ts	49.67742% <0.00000%> (+1.29032%)	⬆️

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Impacted Files	Coverage Δ
packages/api/src/controllers/signing-key.ts	60.67416% <60.67416%> (ø)
packages/api/src/test-helpers.ts	80.85106% <66.66667%> (-0.46762%)	⬇️
packages/api/src/controllers/access-control.ts	100.00000% <100.00000%> (ø)
packages/api/src/store/db.ts	82.22222% <100.00000%> (+0.19974%)	⬆️
packages/api/src/controllers/helpers.ts	49.67742% <0.00000%> (+1.29032%)	⬆️

[victorges]

Awesome! Only some smaller nits or questions :)