feat: add LINE OIDC provider support

[DevRyuki]

What kind of change does this PR introduce?

Feature

This PR adds LINE(https://developers.line.biz/en/docs/line-login/integrate-line-login/) as an external provider.

What is the current behavior?

LINE provider did not exist before.

What is the new behavior?

Adds a first-class LINE OIDC provider, exposes configuration switches in settings, parses LINE ID tokens, and ensures tests cover the new provider so projects can enable LINE sign-in.

https://developers.line.biz/en/docs/line-login/integrate-line-login/

Additional context

[DevRyuki]

Is there anything missing?🤔

[hf]

People have been begging for this for so long. I think we should merge it @supabase/auth wdyt? LINE is huge in Asia, so it goes with our rule that it has to be a huge audience.

[coveralls]

Pull Request Test Coverage Report for Build 19011129672

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 58 of 101 (57.43%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.05%) to 68.048%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/api/token_oidc.go	0	5	0.0%
internal/api/provider/line.go	54	60	90.0%
internal/api/provider/oidc.go	0	32	0.0%

Totals
Change from base Build 19065361991:	-0.05%
Covered Lines:	13941
Relevant Lines:	20487

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💛 - Coveralls