[5.x] Add firstOrfail, firstOr, sole and exists methods to base query builder

[duncanmcclean]

This pull request adds various useful methods to Statamic's base query builder:

• firstOrFail
  • Gets the first result if one exists, otherwise, it throws an exception.
• firstOr
  • Gets the first result if one exists, otherwise, it executes the provided callback.
• sole
  • Gets the first & only item if one exists. It'll throw an exception if no results can be found or if more than 1 result is found.
• exists
  • Returns true if the query returns one or more results.

On the back of #9815, I was thinking a few of Laravel's first/find methods could be added to our "base" query builder since they're useful for everything, not just entries & terms.

[godismyjudge95]

I could use this on the UserQueryBuilder too :)

[duncanmcclean]

I could use this on the UserQueryBuilder too :)

This PR adds the method's to Statamic's base Builder class which gets extended by the other query builders, so they should work for users too.

[godismyjudge95]

I could use this on the UserQueryBuilder too :)

This PR adds the method's to Statamic's base Builder class which gets extended by the other query builders, so they should work for users too.

Oh, I tried to use it in a project with composer patches, and it said method not found. Might be my issue though.

[duncanmcclean]

Are you using flat-file or Eloquent users?

[godismyjudge95]

Are you using flat-file or Eloquent users?

Flat file

[duncanmcclean]

Hmm, this seems to work for me (I'm also using flat-file users):

use Statamic\Facades\User;

User::query()->firstOrFail('ca291c8b-5629-4891-b506-bb2d7d9ad447');