* Auth integration with AppCheck (#10798)
* Auth App check integration without unit testing
* Add Unitest for AppCheck Auth Integration
* Style the format for Auth-Appcheck Integration
* Fix typo in import for FIRAppCheckInterop
* Style this file
* Fix wrong import
* Fix style for this file
* Fix style in this file
* Add Source path for FIRAppCheckInterop
* Add self to async block in Unit Test
* Fix: pass appcheckInterop to request configuration
* style the fixed files
* revert files that are only for local testing
* modify init method to avoid more changes
* remove extra comments
* upload for debug unit test
* Revert Sample changes and add appcheck into unit tests
* Fix issues in FIRAuthRequestConfiguration and typos in unit tests
* fix error loading and revert pod files
* Add spaces to keep style consistent
* pass appCheckToken as URL fragment (#10877)
* pass appCheckToken as URL fragment
* pass appcheck token as url fragments to phone provider
* for test purpose only: commented async function
* test if it is google cloud error
* formatting the file
* formatting the file
* fix comments issues
* remove printing function
* remove unused property
* Adding Unit test for passing appchecktoekn as a url fragment
* add import for FIRAppCheckTokenResultInterop
* Add separate file for FIRFakeAppCheck and Modify accordingly
* add copyright comments for bewly created files
* Add declaration for completion in FIRFakeAppCheck
* add correct param decalaration
* clean FIRFakeAppCheck.h
* add method in FIRAppcheck.h to avoid complaints
* correct copyright info
* fix typo in FIRFakeAppCheck.m
* Recover declarations
* solve comments issues
* Add changes to unit tests for changes in FIRAuthRequestConfiguration
* Add changelog
* Edit changelog
* Add user agent and heartbeat headers to Firebase Auth.
* Add app ID header.
* Fix unit tests.
* Remove user agent and heartbeat headers, as backend support is not yet ready.
* Fix typo.
* Update changelog.
* Fix bug where stored ID token is not updated after linking account with email link.
* Update changelog.
* Fix the Game Center and phone auth flows as well.
* Update upcoming release version number in changelog.
* Add debug logging around token expiration.
* Use FIRLogger instead of NSLog.
* Move log statement.
* Add another log statement when access token is updated.
* Remove deprecated APIs from public header.
* Remove deprecated API implementations.
* Also remove deprecated APIs from FIRUser.
* Update unit tests.
* Update sample app.
* Update changelog.
renkelvin