HS* algs yield invalid key sizes

[alacham]

• jwskate version: 0.5.0
• Python version: 3.7.9
• Operating System: Fedora 31

Description

I wanted to create HS512 key.
Generated key was shorter than expected.

(for required length see) https://www.rfc-editor.org/rfc/rfc7518#section-3.2

What I Did

from jwskate import Jwk, Jwt
print(Jwk.generate_for_alg(alg="HS512"))
{'kty': 'oct', 'k': 'OaFBpH2kogyNz-LvmfYYBw', 'alg': 'HS512'}

I created a PR with a fix #6

[guillp]

Many thanks for the report and PR.
I will fix it a bit differently, and will remove SymmetricJwk.generate_for_alg() override which is unnecessary.

[alacham]

Thanks!