🔧Improve setting when unsigned oidc response

[AntoLC]

Setting optimization

If the OIDC answer with a json, it means the env var OIDC_RP_SIGN_ALGO is not necessary, see:

docs/src/backend/core/authentication/backends.py

Lines 50 to 53 in 9388c8f

	userinfo = user_response.json()
	except ValueError:
	try:
	userinfo = self.verify_token(user_response.text)

We should add more control on this part of code, by setting OIDC_RP_SIGN_ALGO only if we are waiting a signed response.

Basic Suggestion

if(self.get_settings("OIDC_RP_SIGN_ALGO", None)):
 userinfo = self.verify_token(user_response.text)
else:
  userinfo = user_response.json()

[AntoLC]

Issue solved here: suitenumerique/django-lasuite#5

[qbey]

Waiting for #839 to be merged, then the format can be enforced with

OIDC_OP_USER_ENDPOINT_FORMAT = "JWT"  # AUTO, JSON, or JWT