refactor - function return types should be consisten with theiir type hint

.gitignore

@@ -5,4 +5,5 @@ backend/secfit/db.sqlite3
 backend/secfit/htmlcov/
 backend/secfit/.coverage
 backend/secfit/.coveragerc
+.vscode
 .idea

backend/secfit/workouts/models.py

@@ -65,7 +65,7 @@ class Workout(models.Model):
         ordering = ["-date"]
 
     def __str__(self):
-        return self.name
+        return str(self.name)
 
 
 class Exercise(models.Model):
@@ -90,7 +90,7 @@ class Exercise(models.Model):
     unit = models.CharField(max_length=50)
 
     def __str__(self):
-        return self.name
+        return str(self.name)
 
 
 class ExerciseInstance(models.Model):
@@ -139,7 +139,8 @@ class WorkoutFile(models.Model):
         file:    The actual file that's being uploaded
     """
 
-    workout = models.ForeignKey(Workout, on_delete=models.CASCADE, related_name="files")
+    workout = models.ForeignKey(
+        Workout, on_delete=models.CASCADE, related_name="files")
     owner = models.ForeignKey(
         get_user_model(), on_delete=models.CASCADE, related_name="workout_files"
     )
@@ -156,4 +157,4 @@ class RememberMe(models.Model):
     remember_me = models.CharField(max_length=500)
 
     def __str__(self):
-        return self.remember_me
+        return str(self.remember_me)