port over base HTML layout from PHP to FastAPI+Jinja2

+ Mounted static files (at web/html) to /static.
+ Added AURWEB_VERSION to aurweb.config (this is used around HTML
  to refer back to aurweb's release on git.archlinux.org), so we
  need it easily accessible in the Python codebase.
+ Implemented basic Jinja2 partials to put together whole aurweb
  pages. This may be missing some things currently and is a WIP
  until this set is ready to be merged.
+ Added config [options] aurwebdir = YOUR_AUR_ROOT; this configuration
  option should specify the root directory of the aurweb project.
  It is used by various parts of the FastAPI codebase to target
  project directories.

Added routes via aurweb.routers.html:
    * POST /language: Set your session language.
    * GET /favicon.ico: Redirect to /static/images/favicon.ico.
        * Some browsers always look for $ROOT/favicon.ico to get an icon
          for the page being loaded, regardless of a specified "shortcut
          icon" given in a <link> directive.
    * GET /: Home page; WIP.

* Updated aurweb.routers.html.language passes query parameters to
  its next redirection.

When calling aurweb.templates.render_template, the context passed should
be formed via the aurweb.templates.make_context. See
aurweb.routers.html.index for an example of this.

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/asgi.py

@@ -2,13 +2,26 @@ import http
 
 from fastapi import FastAPI, HTTPException
 from fastapi.responses import HTMLResponse
+from fastapi.staticfiles import StaticFiles
 from starlette.middleware.sessions import SessionMiddleware
 
 import aurweb.config
 
-from aurweb.routers import sso
+from aurweb.routers import html, sso
 
+routes = set()
+
+# Setup the FastAPI app.
 app = FastAPI()
+app.mount("/static/css",
+          StaticFiles(directory="web/html/css"),
+          name="static_css")
+app.mount("/static/js",
+          StaticFiles(directory="web/html/js"),
+          name="static_js")
+app.mount("/static/images",
+          StaticFiles(directory="web/html/images"),
+          name="static_images")
 
 session_secret = aurweb.config.get("fastapi", "session_secret")
 if not session_secret:
@@ -17,6 +30,14 @@ if not session_secret:
 app.add_middleware(SessionMiddleware, secret_key=session_secret)
 
 app.include_router(sso.router)
+app.include_router(html.router)
+
+# NOTE: Always keep this dictionary updated with all routes
+# that the application contains. We use this to check for
+# parameter value verification.
+routes = {route.path for route in app.routes}
+routes.update({route.path for route in sso.router.routes})
+routes.update({route.path for route in html.router.routes})
 
 
 @app.exception_handler(HTTPException)