Create joplin.subdomain.conf.sample

[Ogloppi]

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

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Description

I created this reverse proxy conf for the official Docker image of Joplin (or as Joplin calls it 'Joplin Server').
I refer to this as just 'Joplin', because Joplin does not have any other products that are distributed as Docker image.

Benefits of this PR and context

This PR adds yet another service to SWAG for ease of use.
Joplin Server provides a way to host your own instance of Joplin sync server, thus keeping your notes syncronized.

How Has This Been Tested?

Initially I setup Joplin as instructed on Reference 2.
Then, I created this config and used it with SWAG.
Works straight out of the box with default setup.

However, I have not tested (as in uncommented and ran) the following integrations in this config as I currently don't use them:

• ldap
• Authelia
• Authentik
• http auth

Source / References

• Reference 1
  • The Github page for Joplin: https://github.com/laurent22/joplin
• Reference 2
  • Official Joplin Server Docker image: https://hub.docker.com/r/joplin/server
• Reference 3, for more Docker environment variables
  • https://github.com/laurent22/joplin/blob/f938d5f4893c54d5fb22efb8959c295da4f9189a/packages/server/src/env.ts