Enable subdirectory support by default

[mikiher]

Brief summary

Switch to enabling subdirectory support with /audiobookshelf on the server and web client, according to the plan laid out in discussion #3535.

Which issue is fixed?

This finally fixes #385

Users will now be able to set their reverse proxies to proxy /audiobookshelf subdirectory requests

In-depth Description

This is the last step in supporting subdirectory with the existing static site generation approach.

The plan is described in detail in #3535.

As a reminder, this will set a fixed subdirectory of /audiobookshelf on the web client (non-subdirectory paths will get rewritten by the server), and the server will support both subdirectory requests (with /audiobookshelf prefix) and non-subdirectory requests (with no prefix).

Note: Mobile app support for subdirectory is already implemented and checked in with audiobookshelf-app PR #1417, but is pending release of a new version. Other mobile clients that would like to support subdirectory access will likely need to make some changes in the spirit of that PR.

How have you tested this?

This PR just switches the feature on by default.

The many changes required to make this happen were previously tested in respective previous PRs, and were tested again to make sure they still worked now.

One thing I haven't tested properly is the reverse proxy part, since my reverse proxy (on my Synology NAS) doesn't support support subdirectory proxying. I am sure this works well once you set it up on a supporting reverse proxy (like NGINX), but haven't tested this myself.

[advplyr]

Thanks!

[4ch1m]

The new release (Docker container 2.18.0) - which includes/activates this feature - works perfectly fine for me in both the browser and the Android app.

I'm super happy that @mikiher made the effort to implement it. 👍
Again... thank you very much. 🙇

However, I think there are few things that should be revised:

• The environment variable ROUTER_BASE_PATH is (in it's current state) a bit confusing, since it doesn't seem to have any effect at all; or can't actually be used to change the path value.
  (I'm aware that @mikiher explained that the /audiobookshelf path is hardcoded now due to several technical reasons.)
  So why exactly does it still exist?

• The README still says:

  Note: Subfolder paths (e.g. /audiobooks) are not supported yet. See https://github.com/advplyr/audiobookshelf/issues/385`

  This could/should be removed now, I guess.

• The README section containing all reverse proxy setup examples needs to be updated.
  I'm using Apache2 and got everything working with this adjustment:

RewriteRule (.*)/audiobookshelf/?(.*) "ws://127.0.0.1:<audiobookshelf_port>/audiobookshelf/$2" [P,L]

(Not sure if there's a simpler solution though.)

[mikiher]

The new release (Docker container 2.18.0) - which includes/activates this feature - works perfectly fine for me in both the browser and the Android app.

I'm super happy that @mikiher made the effort to implement it. 👍 Again... thank you very much. 🙇

However, I think there are few things that should be revised:

• The environment variable ROUTER_BASE_PATH is (in it's current state) a bit confusing, since it doesn't seem to have any effect at all; or can't actually be used to change the path value.
  (I'm aware that @mikiher explained that the /audiobookshelf path is hardcoded now due to several technical reasons.)
  So why exactly does it still exist?

It is still possible to use the environment variable to change the /audiobookshelf path, but only if you build the code yourself (i.e. set the environment variable then run npm run client). This isn't something most of our users do, hence my use of term "hardcoded".

• The README still says:

  Note: Subfolder paths (e.g. /audiobooks) are not supported yet. See https://github.com/advplyr/audiobookshelf/issues/385`

  This could/should be removed now, I guess.

You're right. We'll remove this.

• The README section containing all reverse proxy setup examples needs to be updated.
  I'm using Apache2 and got everything working with this adjustment:

RewriteRule (.*)/audiobookshelf/?(.*) "ws://127.0.0.1:<audiobookshelf_port>/audiobookshelf/$2" [P,L]

(Not sure if there's a simpler solution though.)

Great! We should definitely provide at least one or two examples of modifying reverse proxy setups for subdirectory support (the existing setups should still work for subdomain). I'm not sure we can be responsible for providing details for every reverse proxy out there, but we definitely should encourage users to share their setups with us and publish them.

You're also welcome to submit a PR to change the documentation, if you like!