[k-nkmr]

Description

When an authentication blocking function rejects an operation,
FirebaseAuthException.code differs between Android and Apple platforms:

• Android: blocking-function-error-response
• Apple: blocking-cloud-function-returned-error

This change maps Android's BLOCKING_FUNCTION_ERROR_RESPONSE marker to
blocking-cloud-function-returned-error, allowing apps to handle this
error with the same code on Android and Apple platforms.

The existing invalid-login-credentials mapping is preserved. The error
code reference and platform differences table are updated accordingly.

Validation

• Updated the existing blocking function test to expect the shared code
  while preserving the JSON error message.
• Added tests for detection from Pigeon details and for preserving
  invalid-login-credentials.
• All 213 tests in firebase_auth_platform_interface pass.
• All Firebase Auth packages pass analysis.
• Workspace analysis (dart run melos run analyze-ci) passes for 59 of
  61 packages. firebase_ai and firebase_ai_example fail because the
  local firebase_options.dart configuration file is missing. These
  failures are unrelated to this change.
• Formatting checks pass for both changed Dart files.
• Device integration testing has not been performed.

Related Issues

• Related to [firebase_auth] Blocking function error code is SCREAMING_SNAKE_CASE on Android instead of kebab-case #18020.
• Follow-up to fix(auth, android): fix an error casing that wasn't consistent accross platforms #18056, which normalized the casing but retained different
  code names on Android and Apple platforms.

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

On Android, apps that check for blocking-function-error-response must
update that check to blocking-cloud-function-returned-error.

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[gemini-code-assist]

Code Review

This pull request normalizes the error code returned on Android for blocking function errors to match the Apple platform error code ('blocking-cloud-function-returned-error'), updating the documentation, exception handling logic, and tests. The review feedback suggests declaring the 'recognizedCodes' map as 'const' instead of 'final' to avoid allocating a new map on every invocation of '_getCustomCode'.

[SelaseKay]

Hi @k-nkmr, thanks for the PR. Could you add an e2e test for this?

[k-nkmr]

@SelaseKay
Added an e2e test for blocking function errors in 9f8eeee. Thanks for the review!