[7.x] Added firstWhereOrFail to Eloquent Builder

[eusonlito]

Extend Eloquent Builder with method firstWhereOrFail to complement firstWhere.

A shortcut for ->where(...)->firstOrFail().

Example: I'm fetching a user by email address:

// Before
User::where('email', 'foo@bar.com')->firstOrFail();

// After
User::firstWhereOrFail('email', 'foo@bar.com');

Implementation Notes:

I only added this to the Eloquent builder for now. As commented on #31089 I have avoided to add this method on the Query builder due failed tests.

Thanks!

[taylorotwell]

I think it's OK as is. Kind of a mouthful as one method.

[eusonlito]

Okey then :)