[FEATURE] Add ability to have multiple identity providers and client profiles

[davidallendj]

OPAAL should have to ability to optionally have multiple identity providers and select which one to use when running the tool:

opaal login --config config.yaml --provider gitlab --client OpenCHAMI

This would allow setting up multiple OAuth2 clients and selecting which login flow to initiate. Allowing this may require changing how the redirect_uri works.

[davidallendj]

This is mostly implemented with #4, but will only use the --client flag which still needs to be added. Currently, opaal with iterate through all the clients in the config until it's able to fetch a valid OIDC server config. This will be changed to only use the first one unless