Feat: add exported error code constants

[hugoecken]

Changes

Summary of changes:

• Added two new public constants:

  • WebAuthErrorCodes
  • CredentialsManagerErrorCodes

• Added a combined constant AuthErrorCodes that merges both sets of codes.

• Added a corresponding union type AuthErrorCode for all possible error type values across the SDK.

• Updated ERROR_CODE_MAP in WebAuthError and CredentialsManagerError to reference the new constants instead of hardcoded strings.

Why this is important:

• This change provides a consistent and type-safe way for SDK users to reference error codes directly from constants.
• Enables IntelliSense / autocompletion for error codes (WebAuthErrorCodes.<CODE>, CredentialsManagerErrorCodes.<CODE>, AuthErrorCodes.<CODE>).
• Reduces the risk of typos and simplifies code maintenance.
• Does not introduce breaking changes — all existing logic and error handling remain identical.

Classes and methods changed:

• WebAuthError: no behavioral change, internal ERROR_CODE_MAP now uses constants.
• CredentialsManagerError: same as above.
• AuthError: new exports added (AuthErrorCodes, AuthErrorCode).

No endpoints or UI are affected by this change.

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References

• This change improves developer experience when consuming SDK error types.
• Inspired by patterns used in other Auth0 SDKs (Web, SPA, and Swift).
• No external support tickets or issues were required for this improvement — this is an internal developer experience enhancement.

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Testing

How reviewers can test:

1. Run the existing unit test suite — no tests should fail.

2. Verify that WebAuthError and CredentialsManagerError still behave as expected (types and mappings).

3. Import and use the new constants in a test or sample app:

   import { AuthErrorCodes } from '../src/models/AuthError';
   
   if (error.type === AuthErrorCodes.NO_CREDENTIALS) {
     ...
   }

4. Confirm TypeScript autocompletion works for:

   • WebAuthErrorCodes.<CODE>
   • CredentialsManagerErrorCodes.<CODE>
   • AuthErrorCodes.<CODE>

Testing notes:

• No new runtime behavior introduced.

• This change affects type definitions and internal mappings only.

• No new dependencies or API calls added.

• This change adds unit test coverage (optional enhancement for type-based validation can be added later).

• This change has been tested locally on the latest React Native SDK setup.

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Checklist

• I have read the [Auth0 general contribution guidelines](https://github.com/auth0/open-source-template/blob/master/GENERAL-CONTRIBUTING.md)
• All existing and new tests complete without errors
• All active GitHub checks have passed
• This change maintains backward compatibility
• New public constants and types are documented and clearly named

[hugoecken]

Now I think its ok, my commit is verified 👍