QueryBuilder multiply and divide support

[faissaloux]

Hello 👋🏻

In this PR I have added multiply and divide to QueryBuilder .

Usage

DB::table('users')->where('name', 'John Doe')->multiply('salary');    // "salary" * 1
DB::table('users')->where('name', 'John Doe')->multiply('salary', 2); // "salary" * 2
DB::table('users')->where('name', 'John Doe')->divide('salary');      // "salary" / 1
DB::table('users')->where('name', 'John Doe')->divide('salary', 2);   // "salary" / 2

Checklist

• Add tests and ensure they pass

[GromNaN]

Thanks for this nice feature that leverage MongoDB update operator.

Could you tell me a bit more about your use-case?

[faissaloux]

Could you tell me a bit more about your use-case?

Case of storing price in cents

We need to get the price converted from cents to USD.

DB::table('products')->where('title', 'socks')->divide('price', 100);

Case of adding tax

DB::table('products')->where('title', 'socks')->multiply('price', 1.2);

[GromNaN]

$amount should not have a default value. Multiplying by 1 is no-op, unless you have extra values.

[GromNaN]

When the field doesn't exist, this operation should not create it as it will always be 0.

Suggested change

	$this->assertEquals(0, $user->salary);
	$this->assertNull($user->salary);