Add serve API to display Svelte pages created by plugins

src/backend/api/serve.py

@@ -0,0 +1,27 @@
+from fastapi.responses import FileResponse
+import logging
+import os
+
+from utils import config, stack
+
+_BUILD_PATH = None
+
+
+async def page(path: str) -> FileResponse:
+    _cache_buildpath()
+    mname = stack.get_caller(depth=2)[0]
+    if not mname.startswith('plugins.plugins.'):
+        logging.error(f'Non-plugin called serve.page() API: "{mname}"')
+        return FileResponse(f'{_BUILD_PATH}/plugins')
+    pname = mname.split('.')[2]
+    fpath = f'{_BUILD_PATH}/plugins/{pname}/{path}.html'
+    if not os.path.exists(fpath):
+        logging.error(f'Plugin page "{path}" for plugin "{pname}" does not exist')
+        return FileResponse(f'{_BUILD_PATH}/dne.html')
+    return FileResponse(fpath)
+
+
+def _cache_buildpath() -> None:
+    global _BUILD_PATH
+    if _BUILD_PATH is None:
+        _BUILD_PATH = config.fetch().get("frontend").get("build_path")