[BE] Change post/comment URLs to include the community #3654

Requirements

• [X] Is this a feature request? For questions or discussions use https://lemmy.ml/c/lemmy_support
• [X] Did you check to see if this issue already exists?
• [X] Is this only a feature request? Do not put multiple feature requests in one issue.
• [X] Is this a backend issue? Use the lemmy-ui repo for UI / frontend issues.

Is your proposal related to a problem?

at first glance, with lemmy URLs I can't tell the context of a URL off the bat. (for example, which community it is in, which post a comment is a part of).

with the URLs for any community post just being {lemmy domain}/post/{post id} and the URLs for any comment being {lemmy domain}/comment/{comment id}

Describe the solution you'd like.

Changing these URLs to include:

• the community that they were posted in
• the post that they are a comment on

The result would be:

• Posts looking like {lemmy domain}/c/{community name}/post/{post id}
• Comments looking like {lemmy domain}/c/{community name}/post/{post id}/comment/{comment id}

Describe alternatives you've considered.

I don't have other ideas for URL formats. This seemed the neatest to me.

Additional context

No response