* Add PKCE support. * Fix tests * Update oauth2.md * Rename usePkce * Fix the BrokenComponent error * Update oauth2.md * Remove isCode variable. Remove uuid4 dependency. * Remove utils functions * Import crypto * Fix tests * Fix the tests * Cleanup * Fix code_challenge generation * Move code challenge and verifier to utils for mocks. Update tests. * Mock the PKCE methods in the utils file properly. * Add missing expect * use target-method spies * Add comments to explain test values. * Get rid of jsrsasign.