added relationship fetch feature

Author: CosmoV

fastapi_jsonapi/__init__.py

@@ -2,32 +2,17 @@
 
 from pathlib import Path
 
-from fastapi import FastAPI
-
-from fastapi_jsonapi.api import RoutersJSONAPI
 from fastapi_jsonapi.exceptions import BadRequest
-from fastapi_jsonapi.exceptions.handlers import base_exception_handler
 from fastapi_jsonapi.exceptions.json_api import HTTPException
 from fastapi_jsonapi.querystring import QueryStringManager
 
+from fastapi_jsonapi.api.application_builder import ApplicationBuilder  # isort: skip
+
 __version__ = Path(__file__).parent.joinpath("VERSION").read_text().strip()
 
 __all__ = [
+    "ApplicationBuilder",
     "BadRequest",
+    "HTTPException",
     "QueryStringManager",
-    "RoutersJSONAPI",
-    "init",
 ]
-
-
-def init(app: FastAPI):
-    """
-    Init the app.
-
-    Processes the application by setting the entities necessary for work.
-
-    Action list:
-    - Registers default exception handlers for exceptions defined
-      in "fastapi_jsonapi.exceptions" module.
-    """
-    app.add_exception_handler(HTTPException, base_exception_handler)