Handle symbol argument in find_or_initialize_with_errors

[MahmoudBakr23]

Fixes #5588

What

find_or_initialize_with_errors now accepts a bare symbol (or string) for required_attributes, in addition to the documented array form.

Why

The method's contract required an array, but didn't enforce it. When a caller passed a bare symbol — as reset_password_by_token does internally when delegating through find_or_initialize_with_error_by — two things broke silently:

1. required_attributes.size returns the character count of the symbol name (e.g. 5 for :email) instead of 1, so the size comparison against attributes.size always fails and the record is never returned even when it exists.
2. required_attributes.each iterates over the symbol as an enumerator of its characters (Ruby 2) or raises NoMethodError (Ruby 3), so the error-building block at the end crashes before adding any validation errors.

The root cause is that the method does no normalisation before using required_attributes as a collection.

Fix

One Array() call at the entry point:

required_attributes = Array(required_attributes)

Array() is the standard Ruby idiom for this normalisation:

• Array([:email]) → [:email] (existing array callers are unaffected)
• Array(:email) → [:email] (bare symbol now works)
• Array("email") → ["email"] (bare string now works)
• Array(nil) → [] (nil is safe)

All existing callers already pass arrays, so there is zero behaviour change for the current codebase.

Tests

Two new cases added to test/models/authenticatable_test.rb, covering the symbol path for both the found and not-found branches:

find_or_initialize_with_errors accepts a single symbol as required_attributes
find_or_initialize_with_errors adds error when given a single symbol and record is not found

Full test run: 9 runs, 10 assertions, 0 failures, 0 errors, 0 skips.