Set allow_url_fopen=0 by default

[KTanAug21]

WHAT AND WHY:
Disable PHP setting allow_url_fopen by default. Include a Dockerfile ENV variable called "PHP_ALLOW_URL_FOPEN" to turn this on ( 1 ) or off( 0 ).

allow_url_fopen has some traces of evil in it, since: it can allow remote code execution. So by default, as suggested by a Fly community member in an email, we disable it for Fly Laravel apps. Of course, there maybe cases that a user may want this setting turned on, hence the ENV variable provided!

HOW
For Laravel apps set to be deployed to Fly.io, create a new remote-file-access.conf template that sets the value of allow_url_fopen based on the value of "PHP_ALLOW_URL_FOPEN" variable. Copy this over to the /etc/php/${PHP_VERSION}/fpm/pool.d for it to be read.

[KTanAug21]

Might need to close this if fly-apps/laravel-docker#12 from laravel-docker is pushed( the PR contains the flag for setting allow_url_fopen value

[kzys]

Does this PR work without fly-apps/laravel-docker#12? Does PHP itself read the environment variable?

[KTanAug21]

Does this PR work without fly-apps/laravel-docker#12? Does PHP itself read the environment variable?

Hi @kzys ! Nope. The reason for adding the flag in the Dockerfile generated is so that it would contain the flag visibly.
Some benefits:
->This way, users will be able to easily see that it can be turned off/on.
->This way, if users actually want it turned on, and expect it to be on (since that's the default value), they'll find that it's actually off! And can immediately set it back on.

[KTanAug21]

Not needed anymore as it is already set up in laravel-docker fly-apps/laravel-docker#12