Add Mongo authMechanism config, make creds optional

[eaglesemanation]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description:

Same as title says, adding more config options for Mongo, specifically to support running with FerretDB instead of Mongo

Benefits of this PR and context:

No need to run old Mongo version

How Has This Been Tested?

Will be tested in my cluster when image is built

Source / References:

[github-actions]

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[LinuxServer-CI]

I am a bot, here is the pushed image/manifest for this PR:

ghcr.io/linuxserver/lspipepr-unifi-network-application:9.0.108-pkg-8d957bf0-dev-6c7856b9e8a85f3abd32a2a568cd4b971875deca-pr-128

[aptalca]

Thanks for the PR, but our users already have a hard enough time getting mongodb set up even with us providing the ready made sh script. This PR would complicate things further and significantly increase our support burden.

Our init steps for setting mongo credentials only work on first run anyway. Users are free to edit system.properties in the config folder to customize the mongo address and params however they like.

[eaglesemanation]

I could theoretically imagine how this change would make it more complicated for users to set up mongo, but I can't figure out how a 15 line change to a shell script is a significant support burden. I made this PR because I had slight inconvenience with current setup process, but if it's really a big deal - feel free to close this at your discretion.

[aptalca]

Support burden: Having to deal with users who can't get it running, and opening GitHub issues, or posting on our forum or discord, going as far as to claim our docs are wrong
If you look through closed issues, you'll see plenty of such claims.