Add FXIOS-14439 [Relay] OAuth token refresh

[mattreaganmozilla]

📜 Tickets

Jira ticket

💡 Description

Adds basic support for automatically refreshing the OAuth token and re-creating the Relay client when authentication token has expired.

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver)
• If adding telemetry, I read the data stewardship requirements and will request a data review
• If adding or modifying strings, I read the guidelines and will request a string review from l10n
• If needed, I updated documentation and added comments to complex code

[mobiletest-ci-bot]

	Messages
📖	Project coverage: 38.08%

🧹 Tidy commit

Just 2 file(s) touched. Thanks for keeping it clean and review-friendly!

🦊 BrowserViewController Check

We’re tracking the size of BrowserViewController.swift to keep it healthy.

• ✨ Change in file size: +2 lines

❌ Per-file test coverage gate

The following changed file(s) are below 35.0% coverage:

File	Coverage	Required
firefox-ios/Client/Frontend/Browser/BrowserViewController/Views/BrowserViewController.swift	29.2%	35.0%
firefox-ios/Client/Frontend/Browser/RelayController.swift	7.2%	35.0%

Client.app: Coverage: 37.1

File	Coverage
BrowserViewController.swift	29.18%	⚠️
RelayController.swift	7.16%	⚠️

Generated by 🚫 Danger Swift against d8d513e

[mattreaganmozilla]

@ih-codes I may have one additional update coming for this, double-checking with AS team on the actual error code we should be checking.

For testing, there is an endpoint you can use to invalidate your OAuth token. DM me if you have any questions. Thank you 🙏