Add support to SOCIAL_AUTH_OIDC_PROMPT and others

[rgaiacs]

This is related to #1124.

This is my first PR to this project. Feedback is welcome, specially regarding

• how to trigger a logging warning?
• how to add a test to this new feature?

If this PR looks good, I will submit others to complete #1124.

[rgaiacs]

A PR with documentation was sent, see python-social-auth/social-docs#288.

[codecov]

Codecov Report

Attention: Patch coverage is 39.21569% with 31 lines in your changes missing coverage. Please review.

Project coverage is 77.69%. Comparing base (4e5ad63) to head (86d79bc).

Files with missing lines	Patch %	Lines
social_core/backends/open_id_connect.py	35.89%	18 Missing and 7 partials ⚠️
social_core/exceptions.py	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1127      +/-   ##
==========================================
- Coverage   77.87%   77.69%   -0.19%     
==========================================
  Files         353      353              
  Lines       10794    10845      +51     
  Branches      471      484      +13     
==========================================
+ Hits         8406     8426      +20     
- Misses       2222     2246      +24     
- Partials      166      173       +7     

Flag	Coverage Δ
unittests	77.69% <39.21%> (-0.19%)	⬇️

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[nijel]

If warnings were meant to indicate errors in the configuration, I think it's better to fail directly. Nobody will notice warnings.

As for the tests, it could check whether the configured parameters are included in the request to the authentication server.

[rgaiacs]

Thanks for the feedback. I expanded to match the list of parameters explicitly mentioned in the Authentication Request section.

I don't implemented all parameters because of my limited knowledge of OpenID.

[rgaiacs]

New exceptions were defined.

[nijel]

AFAIK these should take self as a first parameter.

[nijel]

Let's reuse constructor logic:

Suggested change

	class AuthInvalidParameter(AuthException):
	"""Invalid value for parameter to start or complete the process."""
	def __init__(self, backend, parameter, *args, **kwargs):
	self.parameter = parameter
	super().__init__(backend, *args, **kwargs)
	def __str__(self):
	return f"Invalid value for parameter {self.parameter}"
	class AuthNotImplementedParameter(AuthException):
	"""Optional parameter not implemented to start or complete the process."""
	def __init__(self, backend, parameter, *args, **kwargs):
	self.parameter = parameter
	super().__init__(backend, *args, **kwargs)
	class AuthInvalidParameter(AuthMissingParameter):
	"""Invalid value for parameter to start or complete the process."""
	def __str__(self):
	return f"Invalid value for parameter {self.parameter}"
	class AuthNotImplementedParameter(AuthMissingParameter):
	"""Optional parameter not implemented to start or complete the process."""