fix: return a specific error message for email & phone validation errors

[jonas-jonas]

Related issue(s)

Fixes #4192

Checklist

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Further Comments

[jonas-jonas]

This does not pass the tests, because somewhere along the chain we now escape \\ twice, which breaks one test. I am not sure how to fix, yet.

Not equal:
	expected: "\\ is not a valid email address"
	actual  : "\\\\ is not a valid email address"