feat: add email adapter DSN parsing

[TorstenDittmann]

Summary

• add Email::fromDsn() to create email adapters from DSN strings
• support smtp, smtps, resend, sendgrid, and mailgun schemes with strict validation
• document the format and cover parsing with dedicated unit tests

Testing

• ./vendor/bin/phpunit tests/Messaging/Adapter/Email/DsnTest.php
• ./vendor/bin/phpunit tests/Messaging/MessengerTest.php
• ./vendor/bin/pint --preset psr12 --test

[greptile-apps]

Greptile Summary

This PR adds Email::fromDsn() to the abstract email adapter, supporting smtp, smtps, resend, sendgrid, and mailgun schemes with URL-component extraction, per-option type/value parsing, and accompanying unit tests and README documentation. The implementation is clean and well-structured. A few validation gaps noted in prior review rounds (failing test_rejects_malformed_smtp_dsn assertion, absent port-range check, query-string port precedence) remain unaddressed.

Confidence Score: 4/5

Safe to merge after addressing the previously flagged failing test assertion and the minor validation gaps.

No new P0/P1 findings from this pass. Score is held at 4 rather than 5 because open items from prior review rounds — the test_rejects_malformed_smtp_dsn assertion mismatch that will cause a test failure, the missing TCP port-range guard, and the counter-intuitive query-string port precedence — are still present and unresolved.

tests/Messaging/Adapter/Email/DsnTest.php (wrong exception message assertion), src/Utopia/Messaging/Adapter/Email.php (port range and precedence)

Important Files Changed

Filename	Overview
src/Utopia/Messaging/Adapter/Email.php	Adds fromDsn() factory with helper parse methods; port range validation gap and query-string port precedence noted in prior threads remain unresolved.
tests/Messaging/Adapter/Email/DsnTest.php	Adds DSN unit tests; test_rejects_malformed_smtp_dsn asserts the wrong exception message and will fail (noted in prior thread, unresolved).
README.md	Adds DSN usage examples for all five supported schemes; examples are correct and consistent with the implementation.

_{Reviews (2): Last reviewed commit: "feat: add email adapter DSN parsing" | Re-trigger Greptile}

[greptile-apps]

Query-string port silently overrides URL port

The precedence $query['port'] > $parts['port'] > scheme-default means smtp://host:587?port=25 resolves to port 25. Most DSN parsers treat the URL authority port as authoritative. This is a subtle gotcha worth a brief inline comment, or consider flipping the precedence to URL port > query port > scheme default.