Make path to /var/www/ood/apps apps directory easily configurable

[ericfranz]

Currently the knowledge of where these apps are located is duplicated between nginx_stage and the dashboard app.

As a result, while we could change the location of these apps in nginx_stage.yml the dashboard has the original paths hardcoded:

• dev: https://github.com/OSC/ondemand/blob/3b10306e4cb94260d40bf642bd28f0e409e67fa6/apps/dashboard/app/apps/dev_router.rb#L28-L30
• sys: https://github.com/OSC/ondemand/blob/3b10306e4cb94260d40bf642bd28f0e409e67fa6/apps/dashboard/app/apps/sys_router.rb#L31-L33
• usr: https://github.com/OSC/ondemand/blob/3b10306e4cb94260d40bf642bd28f0e409e67fa6/apps/dashboard/app/apps/usr_router.rb#L59-L84

Removing this duplication would help.

Another approach would be to shift the scanning of apps users can launch to nginx_stage, generating the app configs dynamically like we generate the nginx_stage config.

┆Issue is synchronized with this Asana task by Unito

[Oglopf]

This issue should be labeled bug as we say the sys path can be configured in our docs, but it can't. We've also had a user bring this to our attention on the discourse and request that it get fixed.

https://discourse.openondemand.org/t/change-sys-apps-path/3425/3

Adding some tags to prioritize the work.