Expose more advanced OIDAuthorizationRequest configuration options.

[jsamol]

The current interface allows developers to configure their authorization requests on a very basic level with just clientId, audience, hosted domain and login_hint, leaving more advanced parameters outside of their control. However, OIDAuthorizationRequest exposes a more complex initializer than the one currently in use:

- (instancetype)initWithConfiguration:(OIDServiceConfiguration *)configuration
 clientId:(NSString *)clientID
 clientSecret:(nullable NSString *)clientSecret
 scope:(nullable NSString *)scope
 redirectURL:(NSURL *)redirectURL
 responseType:(NSString *)responseType
 state:(nullable NSString *)state
 nonce:(nullable NSString *)nonce
 codeVerifier:(nullable NSString *)codeVerifier
 codeChallenge:(nullable NSString *)codeChallenge
 codeChallengeMethod:(nullable NSString *)codeChallengeMethod
 additionalParameters:(nullable NSDictionary<NSString *, NSString *> *)additionalParameters

which (in theory) means, that the limitation is only in GIDConfiguration.

Since we're talking about a piece of software made by developers for developers, I believe making it more flexible for non-standard and advanced use cases can only improve it.