Cache challenge data for faster loading of /api/v1/challenges (#2232)

* Improve response time of `/api/v1/challenges` and `/api/v1/challenges/[challenge_id]/solves`
* Rewrite and remove _build_solves_query to make it cacheable
* Closes #2209

tests/cache/test_challenges.py

@@ -0,0 +1,128 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from CTFd.models import Users
+from tests.helpers import (
+    create_ctfd,
+    destroy_ctfd,
+    login_as_user,
+    register_user,
+    simulate_user_activity,
+)
+
+
+def test_adding_challenge_clears_cache():
+    """
+    Test that when we add a challenge, it appears in our challenge list
+    """
+    app = create_ctfd()
+    with app.app_context():
+        register_user(app)
+
+        with login_as_user(app) as client, login_as_user(
+            app, name="admin", password="password"
+        ) as admin:
+            req = client.get("/api/v1/challenges")
+            data = req.get_json()
+            assert data["data"] == []
+
+            challenge_data = {
+                "name": "name",
+                "category": "category",
+                "description": "description",
+                "value": 100,
+                "state": "visible",
+                "type": "standard",
+            }
+
+            r = admin.post("/api/v1/challenges", json=challenge_data)
+            assert r.get_json().get("data")["id"] == 1
+
+            req = client.get("/api/v1/challenges")
+            data = req.get_json()
+            assert data["data"] != []
+    destroy_ctfd(app)
+
+
+def test_deleting_challenge_clears_cache_solves():
+    """
+    Test that deleting a challenge clears the cached solves for the challenge
+    """
+    app = create_ctfd()
+    with app.app_context():
+        register_user(app)
+        user = Users.query.filter_by(id=2).first()
+        simulate_user_activity(app.db, user)
+        with login_as_user(app) as client, login_as_user(
+            app, name="admin", password="password"
+        ) as admin:
+            req = client.get("/api/v1/challenges")
+            data = req.get_json()["data"]
+            challenge = data[0]
+            assert challenge["solves"] == 1
+            from CTFd.utils.challenges import (
+                get_solves_for_challenge_id,
+                get_solve_counts_for_challenges,
+            )
+
+            solves = get_solves_for_challenge_id(1)
+            solve_counts = get_solve_counts_for_challenges()
+            solves_req = client.get("/api/v1/challenges/1/solves").get_json()["data"]
+            assert len(solves_req) == 1
+            assert len(solves) == 1
+            assert solve_counts[1] == 1
+
+            r = admin.delete("/api/v1/challenges/1", json="")
+            assert r.status_code == 200
+
+            solve_counts = get_solve_counts_for_challenges()
+            solves = get_solves_for_challenge_id(1)
+            r = client.get("/api/v1/challenges/1/solves")
+            assert r.status_code == 404
+            assert len(solves) == 0
+            assert solve_counts.get(1) is None
+    destroy_ctfd(app)
+
+
+def test_deleting_solve_clears_cache():
+    """
+    Test that deleting a solve clears out the solve count cache
+    """
+    app = create_ctfd()
+    with app.app_context():
+        register_user(app)
+        user = Users.query.filter_by(id=2).first()
+        simulate_user_activity(app.db, user)
+        with login_as_user(app) as client, login_as_user(
+            app, name="admin", password="password"
+        ) as admin:
+            req = client.get("/api/v1/challenges")
+            data = req.get_json()["data"]
+            challenge = data[0]
+            assert challenge["solves"] == 1
+            from CTFd.utils.challenges import (
+                get_solves_for_challenge_id,
+                get_solve_counts_for_challenges,
+            )
+
+            solves = get_solves_for_challenge_id(1)
+            solve_counts = get_solve_counts_for_challenges()
+            solves_req = client.get("/api/v1/challenges/1/solves").get_json()["data"]
+            assert len(solves_req) == 1
+            assert len(solves) == 1
+            assert solve_counts[1] == 1
+
+            r = admin.get("/api/v1/submissions/6", json="")
+            assert r.get_json()["data"]["type"] == "correct"
+            r = admin.delete("/api/v1/submissions/6", json="")
+            assert r.status_code == 200
+            r = admin.get("/api/v1/submissions/6", json="")
+            assert r.status_code == 404
+
+            solve_counts = get_solve_counts_for_challenges()
+            solves = get_solves_for_challenge_id(1)
+            solves_req = client.get("/api/v1/challenges/1/solves").get_json()["data"]
+            assert len(solves_req) == 0
+            assert len(solves) == 0
+            assert solve_counts.get(1) is None
+    destroy_ctfd(app)