[10.x] Update DatabaseRule to handle Enums for simple where clause

[calebdw]

Hello!

This PR updates the DatabaseRule trait (used by Rule::unique and others) to automatically cast Enums to their value like the Query class does. For example, this throws an exception:

Rule::unique(<class>)->where('status', Enum::Case);

whereas this does work in a normal query:

Model::query()->where('status', Enum::Case);

Thanks!

[taylorotwell]

Does it work for whereIn?

[calebdw]

@taylorotwell,

whereIn calls are being forwarded to the underlying query using a closure (so therefore it works by default):

framework/src/Illuminate/Validation/Rules/DatabaseRule.php

Lines 151 to 156 in 8eb6ae8

	public function whereIn($column, $values)
	{
	return $this->where(function ($query) use ($column, $values) {
	$query->whereIn($column, $values);
	});
	}

The reason why it was throwing an exception for where is because the simple wheres are being converted to their string equivalents instead of also being forwarded:

framework/src/Illuminate/Validation/Rules/DatabaseRule.php

Line 101 in 8eb6ae8

$this->wheres[] = compact('column', 'value');

framework/src/Illuminate/Validation/Rules/DatabaseRule.php

Lines 226 to 231 in 8eb6ae8

	protected function formatWheres()
	{
	return collect($this->wheres)->map(function ($where) {
	return $where['column'].','.'"'.str_replace('"', '""', $where['value']).'"';
	})->implode(',');
	}

I just made the easy change by converting the enum to it's backed value before it's ultimately converted to a string...it might be a better idea to remove the where string conversion/reparsing and just send everything to the underlying query.