Multiple mod versions download/upload & channel customization

[Niwer1525]

It may be useful to add multiple versions storage on the server.
For example instead of saving /services_updates/mod.jar we may add a version field and save it to /services_update/mod/1.0.0.jar so users can download the version they want if they want to.

This will be native when release on modrinth, and when released on modrinth this current system will be deleted or hidden.

[Niwer1525]

Also it would be useful to finish the channel system so the user can download from all existing channels (would be provided by javalin).

Note : Channel would only be provided if one or multiple files exists for that channel.