Update README.md mongo init instructions

[clee]

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

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Description:

Update the instructions for initializing MongoDB, as the provided instructions led to errors when I followed them.

Benefits of this PR and context:

closes #12

How Has This Been Tested?

• I started by backing up my existing unifi controller, so I could migrate to this new image.
• Pulled tag 7.5.174, c91e20ea07438
• Followed provided instructions on creating two mongoDB users, one for the main unifi database and one for the unifi_stats database. This created two separate users in mongoDB, unifi.unifi and unifi_stats.unifi, with distinct UUIDs.
• Unifi was able to connect to the unifi database in mongo and attempt startup, but produced errors in the unifi server.log, not authorized on unifi_stat to execute command { listCollections: 1.
• Updating the unifi.unifi user to add { 'role': 'readWrite', 'db': 'unifi_stat' } allows the unifi server to start up successfully, but attempting to import my backup produced a new error in server.log: not authorized on unifi to execute command { dropDatabase: 1, $db: "unifi". Apparently importing a backup requires the ability to drop the database.
• So I updated the roles again, this time using dbOwner instead of readWrite for both databases, and finally was able to successfully import my backup and run the unifi-network-application image.

Source / References:

None

[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:7.5.176-pkg-3f48ad74-dev-514af1526bd5fbc2d60a46f056f7ab2802798411-pr-19

[thespad]

I didn't encounter the dbOwner requirement when performing a restore, but there's no real harm in using it over readWrite in this instance so I've no problem updating the readme. However, you need to make the changes to readme-vars.yml as per the contributing guidelines, because the readme.md is generated on build and any changes made to it will be overwritten.

[clee]

I didn't encounter the dbOwner requirement when performing a restore, but there's no real harm in using it over readWrite in this instance so I've no problem updating the readme. However, you need to make the changes to readme-vars.yml as per the contributing guidelines, because the readme.md is generated on build and any changes made to it will be overwritten.

Changes made to readme-vars.yml and pushed.

[LinuxServer-CI]

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

ghcr.io/linuxserver/lspipepr-unifi-network-application:7.5.176-pkg-3f48ad74-dev-5d4ea38d1e39be6186572b99f5ce8bc42743a169-pr-19