[#1349] Basic Cookie Authentication (#1498)

* [#1349] Stub basic cookie authentication

* [#1349] Basic login page

Also adjusts WebView header color and shadow to match WebUI. WebUI uses
a background-image gradient to change the perceived color, which was not
noticed originally.

* [#1349] Handle login post

* [#1349] Redirect to previous URL

* [#1349] Return a basic 401 for api endpoints

Instead of redirecting to a visual login page, API should just indicate
the bad state

* Use more appropriate 303 redirect

* Update server/src/main/kotlin/suwayomi/tachidesk/server/JavalinSetup.kt

Co-authored-by: Mitchell Syer <Syer10@users.noreply.github.com>

* Update server/src/main/kotlin/suwayomi/tachidesk/server/JavalinSetup.kt

Co-authored-by: Mitchell Syer <Syer10@users.noreply.github.com>

* Lint

* Transition to AuthMode enum with migration path

* Make basicAuthEnabled auto property, Lint

* ConfigManager: Make sure to re-parse the config after migration

* basicAuth{Username,Password} -> auth{Username,Password}

* Lint

* Update server settings backup model

* Update comment

* Minor cleanup

* Improve backup legacy settings fix

* Lint

* Simplify config value migration

---------

Co-authored-by: Mitchell Syer <Syer10@users.noreply.github.com>

server/src/main/kotlin/suwayomi/tachidesk/graphql/mutations/SettingsMutation.kt

@@ -155,6 +155,9 @@ class SettingsMutation {
         updateSetting(settings.updateMangas, serverConfig.updateMangas)
 
         // Authentication
+        updateSetting(settings.authMode, serverConfig.authMode)
+        updateSetting(settings.authUsername, serverConfig.authUsername)
+        updateSetting(settings.authPassword, serverConfig.authPassword)
         updateSetting(settings.basicAuthEnabled, serverConfig.basicAuthEnabled)
         updateSetting(settings.basicAuthUsername, serverConfig.basicAuthUsername)
         updateSetting(settings.basicAuthPassword, serverConfig.basicAuthPassword)