feat: Add message_size_limit option

[nassoor]

Description of the change

This adds the message_size_limit option to enable changing the default value.

Motivation and Context

To enable sending larger messages

How Has This Been Tested?

Tested the change with a value of 34000000 (34MB)

Types of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Documentation (adding or updating documentation)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My change requires a change to the documentation and I have updated the documentation accordingly.
• [x] My change adds a new configuration variable and I have updated the .env.example file accordingly.

And lastly, many thanks for taking your time to help us improve this project !

[itsalljustdata]

Winner! I was just about to do a PR for this myself....

until this gets merged, i've modified my docker run "--health-cmd" value to be --health-cmd 'postconf message_size_limit=$MESSAGE_SIZE_LIMIT && postfix status'

[juanluisbaptiste]

Hi @nassoor, thanks for the PR, but it currently needs rebasing.

[nassoor]

Done

[juanluisbaptiste]

@nassoor Sorry for the late reply, thanks for the rebasing but I merged a previous PR and it needs again rebasing. Please rebase against master again and I will merge inmediately. TY

[nassoor]

Done 👍

[juanluisbaptiste]

@nassoor there is still something missing as the PR still says it cannot be rebased due to conflicts.

[nassoor]

GitHub does not show me anything like that, quite the opposite.

https://github.com/juanluisbaptiste/docker-postfix/compare/master...nassoor:master

[nassoor]

I can recreate the PR if necessary.

[juanluisbaptiste]

This is what appears on the PR:

[nassoor]

I will recreate.