DOCSP-36792: Add default database connection admonition

[norareidy]

JIRA - https://jira.mongodb.org/browse/DOCSP-36792
Staging -
https://preview-mongodbnorareidy.gatsbyjs.io/laravel/DOCSP-36792/quick-start/configure-mongodb/
https://preview-mongodbnorareidy.gatsbyjs.io/laravel/DOCSP-36792/query-builder/

Checklist

• Add tests and ensure they pass
• Add an entry to the CHANGELOG.md file
• Update documentation for new features

[rustagir]

lgtm

[GromNaN]

This is wrong, the DB facade can be used for any connection. Each model class specifies the connection it uses (for Eloquent builder), and the connection name can be specified before creating a query builder:

DB::connection('mongodb')->collection('users')->...

[GromNaN]

If people want to update their default connection, it might be in the env var DB_CONNECTION in the .env file.

[norareidy]

This line should set the default connection to MongoDB even if the DB_CONNECTION variable is set to something else in .env. But I updated the admonition (in query-builder.txt) to give two options on how to set MongoDB as the connection, if that helps clarify

[GromNaN]

I remain convinced that this is the not the right way to change the default connection. @alcaeus any opinion?

[alcaeus]

Laravel's default configuration uses env variables, and I agree that we shouldn't deviate too far from this.

[norareidy]

Okay, I changed these code snippets back to using env variables. Since we don't explain the .env file or its variables in the quick start, I made a ticket to add this info.

[alcaeus]

Laravel's default configuration uses env variables, and I agree that we shouldn't deviate too far from this.

[alcaeus]

As the connection string is likely to differ between environments (e.g. dev, staging, prod), we should stick with the Laravel default of providing this in an environment variable.

Suggested change

	'dsn' => '<connection string>',
	'dsn' => env('DB_URI', '<connection string>'),

[alcaeus]

This should mention that one should pass the connection name (for which we use "mongodb" in our examples). Also, I suggest using a code snippet for this purpose:

Suggested change

	If MongoDB is not your application's default database, you can use the ``DB::connection()`` method
	to specify a MongoDB connection. Pass a value of ``"mongodb"`` to the ``connection()`` method.
	If MongoDB is not your application's default database, you can use the ``DB::connection()`` method
	to specify a MongoDB connection. Pass a the name of the connection to the ``connection()`` method:
	.. code-block:: php
	$connection = DB::connection('mongodb');

Changes addressed, deferring to Jérôme for final review.