Add configurable base path for reverse proxy use (#169)

* ui: Refactor routing functions into Router record
* ui: Store base URI in AppConfig
* ui: Use basePath in Router functions
* backend: Add Web.BasePath config option and update routes
* Tweaks to get SPA to bootstrap basePath configured
* ui: basePath support for apis/serve
* ui: basePath support for message monitor
* web: Redirect requests to / when basePath configured
* doc: add basepath to config.md
* Closes #107

ui/src/Data/Session.elm

@@ -18,6 +18,7 @@ import Data.AppConfig as AppConfig exposing (AppConfig)
 import Json.Decode as D
 import Json.Decode.Pipeline exposing (optional)
 import Json.Encode as E
+import Route exposing (Router)
 import Time
 import Url exposing (Url)
 
@@ -27,6 +28,7 @@ type alias Session =
     , host : String
     , flash : Maybe Flash
     , routing : Bool
+    , router : Router
     , zone : Time.Zone
     , config : AppConfig
     , persistent : Persistent
@@ -50,6 +52,7 @@ init key location config persistent =
     , host = location.host
     , flash = Nothing
     , routing = True
+    , router = Route.newRouter config.basePath
     , zone = Time.utc
     , config = config
     , persistent = persistent
@@ -62,6 +65,7 @@ initError key location error =
     , host = location.host
     , flash = Just (Flash "Initialization failed" [ ( "Error", error ) ])
     , routing = True
+    , router = Route.newRouter ""
     , zone = Time.utc
     , config = AppConfig.default
     , persistent = Persistent []