Utilize redirect_uri_path from config

[yorinasub17]

Hello!

I noticed that the config schema had the params for redirect_uri_path, but the plugin wasn't passing it through to lua-resty-openidc. This updates it so that it will utilize the config if it is set, and otherwise fallback to the original behavior.

My use case for this is that I am trying to integrate with identityserver.io, which has very strict restrictions on the redirect_uri (for good reasons), and thus it becomes near impossible because all API uris must be registered. This allows for registering just a single endpoint that is used as the callback, which will autoforward to the originally requested uri as done by lua-resty-openidc.

[coveralls]

Pull Request Test Coverage Report for Build 58

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 54.795%

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Totals
Change from base Build 52:	0.0%
Covered Lines:	1040
Relevant Lines:	1898

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💛 - Coveralls