Merge branch 'dev' into feat/semester-update

# Conflicts:
#	app/routes/api_v1/endpoints/courses.py
#	app/routes/api_v1/endpoints/semesters.py
#	app/schemas/__init__.py

app/routes/api_v1/endpoints/courses.py

 from typing import List
 
 from cachetools import TTLCache, cached
-from fastapi import APIRouter, Depends, Query, Path
+from fastapi import APIRouter, Depends, Query, Path, HTTPException
 
 from app import schemas
 from app.data.brokers import Broker, DatabaseBroker
@@ -30,11 +30,14 @@ def list_all_courses_of_semester(semesterId: int = Query(..., example=1),
     return broker.get_all_courses_of_semester(semesterId)
 
 
-@router.get("/{courseId}", response_model=schemas.Course)
+@router.get("/{courseId}", response_model=schemas.Course, responses={404: {"model": schemas.DetailMessage}})
 def retrieve_information_of_a_course(semesterId: int = Query(..., example=1),
                                      courseId: str = Path(..., example="L.079.05401"),
                                      broker: Broker = Depends(get_database_broker)):
     """
     Querries course by id with all small groups and appointments.
     """
-    return broker.find_course_by_id(semesterId, courseId)
+    course = broker.find_course_by_id(semesterId, courseId)
+    if not course:
+        raise HTTPException(status_code=404, detail="Course not found")
+    return course

app/routes/api_v1/endpoints/semesters.py

+import os
 from typing import List
 
 from fastapi import APIRouter, Depends
@@ -23,3 +24,8 @@ def see_newest_semesters(broker: DatabaseBroker = Depends(get_database_broker)):
     Returns newest semester of all semesters with same name.
     """
     return broker.get_newest_semesters()
+
+
+@router.get("/revision", response_model=int)
+def see_current_data_revision():
+    return os.environ.get("REVISION", 1)

app/schemas/__init__.py

 from .course import Course, Appointment, SmallGroup, CourseList, CourseWithoutAppointments, Semester, SemesterList, \
     SemesterWithoutCourses, SemesterWithoutCoursesButId
+from .message import DetailMessage

app/schemas/message.py

+from pydantic import BaseModel
+
+
+class DetailMessage(BaseModel):
+    detail: str
+
+    class Config:
+        schema_extra = {
+            "example": {
+                "detail": "something with XY"
+            }
+        }