Add SAML Login Flow

[chownces]

Description

• [x] Added SAML flow. Some workarounds needed, since SAML does not play well with modern SPA sites.
• [x] Separated the Login component logic into new components

I will work on some documentation outlining the various auth flows in our application soon.

To be merged together with https://github.com/source-academy/backend/pull/990

Type of change

• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How to test

TODO: add instructions for local setup and configuration

Checklist

• [x] I have tested this code
• [ ] I have updated the documentation

[coveralls]

Pull Request Test Coverage Report for Build 9052804419

Details

• 46 of 56 (82.14%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 31.604%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/pages/login/LoginPage.tsx	11	13	84.62%
src/commons/utils/AuthHelper.ts	1	9	11.11%
<!--	Total:	46	56	82.14%	-->

Totals
Change from base Build 9052785407:	0.01%
Covered Lines:	4937
Relevant Lines:	14707

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💛 - Coveralls