Compensation action

* adds compensation action to compensation detail view
* adds adding/removing logic for compensation action
* adds bootstrap style to select fields in forms
* refactors UnitEnum into UnitChoices using models.TextChoices (Django 3.x)
* adds translations

compensation/models.py

@@ -11,6 +11,7 @@ from django.core.validators import MinValueValidator, MaxValueValidator
 from django.db import transaction
 from django.utils import timezone
 from django.utils.timezone import now
+from django.utils.translation import gettext_lazy as _
 
 from compensation.settings import COMPENSATION_IDENTIFIER_LENGTH, COMPENSATION_IDENTIFIER_TEMPLATE
 from intervention.models import Intervention, ResponsibilityData
@@ -63,18 +64,45 @@ class CompensationState(UuidModel):
         return "{} | {} m²".format(self.biotope_type, self.surface)
 
 
+class UnitChoices(models.TextChoices):
+    """
+    Predefines units for selection
+    """
+    cm = "cm", _("cm")
+    m = "m", _("m")
+    km = "km", _("km")
+    qm = "qm", _("m²")
+    ha = "ha", _("ha")
+    st = "pcs", _("Pieces")  # pieces
+
+
 class CompensationAction(BaseResource):
     """
     Compensations include actions like planting trees, refreshing rivers and so on.
     """
     action_type = models.CharField(max_length=500, null=True, blank=True)
     amount = models.FloatField()
-    unit = models.CharField(max_length=100, null=True, blank=True)
+    unit = models.CharField(max_length=100, null=True, blank=True, choices=UnitChoices.choices)
     control = models.ForeignKey(CompensationControl, on_delete=models.SET_NULL, null=True, blank=True)
 
     def __str__(self):
         return "{} | {} {}".format(self.action_type, self.amount, self.unit)
 
+    @property
+    def unit_humanize(self):
+        """ Returns humanized version of enum
+
+        Used for template rendering
+
+        Returns:
+
+        """
+        choices = UnitChoices.choices
+        for choice in choices:
+            if choice[0] == self.unit:
+                return choice[1]
+        return None
+
 
 class AbstractCompensation(BaseObject):
     """