Validate bearer token through OIDC/OAuth endpoint

[uniqueg]

Is your feature request related to a problem? Please describe.
Currently, when the security:authorization_required switch is set in the config file, the passed JSON Web Token (JWT) bearer token is base64-decoded and it's signature verified against an identity provider's (IdP) public key that is also hard-coded_ in the config file (under security:jwt:public_key). This is not a very flexible solution.

Describe the solution you'd like
A service call to an OIDC endpoint should be added that dynamically obtains a IdP's public key (otherwise keeping the current solution) via the https://[base-server-url]/jwks.json endpoint OR validates the token via the token introspection endpoint of the form https://[base-server-url]/token/introspect. The base-server-url can be obtained from a JWT by base64-decoding and extracting the iss claim.

Note that since the second solution (accessing the token introspection endpoint) may be more robust/safe, but usually requires a client secret, which right now we do not have and possibly do not want to have for every possible IdP (discussion point with ELIXIR Cloud & AAI group) this is currently not the preferred solution.

Describe alternatives you've considered
N/A

Additional context
The current handling of bearer tokens is done in wes_elixir/security/decorators.py, so this would be the entry point and likely the only file requiring modifications to implement the suggested changes.