Added basic structure for the fast api endpoints as per the task

app.py

@@ -0,0 +1,38 @@
+from dotenv import load_dotenv
+
+load_dotenv()
+
+from fastapi import FastAPI
+from models import Action, Observation, StepResult
+
+app = FastAPI(title="Sieve")
+
+
+@app.get("/")
+def root():
+    pass
+
+
+@app.post("/reset", response_model=Observation)
+def reset(task_id: str = "email_classificaiton"):
+    pass
+
+
+@app.post("/step", response_model=StepResult)
+def step(action: Action):
+    pass
+
+
+@app.get("/state")
+def state():
+    pass
+
+
+@app.get("/tasks")
+def list_tasks():
+    pass
+
+
+@app.get("/grader")
+def grader():
+    pass