* factor out GetSubpathFromConfig
* mv web/subpath.go to utils/subpath.go
* serve up web, api and ws on /subpath if configured
* pass config to utils.RenderWeb(App)?Error
This allows the methods to extract the configured subpath and redirect
to the appropriate `/subpath/error` handler.
* ensure GetSubpathFromConfig returns trailing slashes deterministically
* fix error 404 handling
* redirect /subpath to /subpath/
This is necessary for the static handler to match, otherwise none of the
registered routes find anything. This also makes it no longer necessary
to add trailing slashes in the root router.
* PLT-7468 Moved more errors to use error types
* PLT-7468 Moved 404 error page to use error types
* Made helper function for rendering external links on error page
* Implement POST /oauth/apps endpoint for APIv4
* Implement GET /oauth/apps endpoint for APIv4
* Implement GET /oauth/apps/{app_id} and /oauth/apps/{app_id}/info endpoints for APIv4
* Refactor API version independent oauth endpoints
* Implement DELETE /oauth/apps/{app_id} endpoint for APIv4
* Implement /oauth/apps/{app_id}/regen_secret endpoint for APIv4
* Implement GET /user/{user_id}/oauth/apps/authorized endpoint for APIv4
* Implement POST /oauth/deauthorize endpoint
