migrate examinations to generic model (and start adding mangament)

generic/models.py

@@ -1,5 +1,6 @@
 from collections import defaultdict
 import json
+import os
 from typing import Tuple
 from django.contrib.auth.mixins import LoginRequiredMixin
 from django.db import models
@@ -42,6 +43,11 @@ def findMiddle(input_list):
     else:
         return input_list[int(middle)]
 
+class Modality(models.Model):
+    modality = models.CharField(max_length=200)
+
+    def __str__(self):
+        return self.modality
 
 class Plane(models.Model):
     plane = models.CharField(max_length=200, unique=True)
@@ -66,6 +72,8 @@ class Contrast(models.Model):
 class Examination(models.Model):
     examination = models.CharField(max_length=200, unique=True)
 
+    modality = models.ForeignKey(Modality, on_delete=models.SET_NULL, null=True)
+
     def __str__(self):
         return self.examination