refactor: migrate to question sets for person qs

This means we're starting to use the same system for person questions
as for relationship questions

people/models/person.py

@@ -1,10 +1,12 @@
 import logging
+import typing
 
 from django.conf import settings
 from django.contrib.auth.models import AbstractUser
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.urls import reverse
+from django.utils.text import slugify
 from django.utils.translation import gettext_lazy as _
 
 from django_countries.fields import CountryField
@@ -18,9 +20,11 @@ logger = logging.getLogger(__name__)  # pylint: disable=invalid-name
 __all__ = [
     'User',
     'Organisation',
-    'Role',
     'Theme',
+    'PersonQuestion',
+    'PersonQuestionChoice',
     'Person',
+    'PersonAnswerSet',
 ]
 
 
@@ -36,7 +40,7 @@ class User(AbstractUser):
         """
         return hasattr(self, 'person')
 
-    def send_welcome_email(self):
+    def send_welcome_email(self) -> None:
         """Send a welcome email to a new user."""
         # Get exported data from settings.py first
         context = settings_export(None)
@@ -71,16 +75,6 @@ class Organisation(models.Model):
         return self.name
 
 
-class Role(models.Model):
-    """
-    Role which a :class:`Person` holds within the project.
-    """
-    name = models.CharField(max_length=255, blank=False, null=False)
-
-    def __str__(self) -> str:
-        return self.name
-
-
 class Theme(models.Model):
     """
     Project theme within which a :class:`Person` works.
@@ -91,6 +85,79 @@ class Theme(models.Model):
         return self.name
 
 
+class PersonQuestion(models.Model):
+    """Question which may be asked about a person."""
+    class Meta:
+        ordering = [
+            'order',
+            'text',
+        ]
+
+    #: Version number of this question - to allow modification without invalidating existing data
+    version = models.PositiveSmallIntegerField(default=1,
+                                               blank=False, null=False)
+
+    #: Text of question
+    text = models.CharField(max_length=255,
+                            blank=False, null=False)
+
+    #: Position of this question in the list
+    order = models.SmallIntegerField(default=0,
+                                     blank=False, null=False)
+
+    @property
+    def choices(self) -> typing.List[typing.List[str]]:
+        """
+        Convert the :class:`PersonQuestionChoice`s for this question into Django choices.
+        """
+        return [
+            [choice.pk, str(choice)] for choice in self.answers.all()
+        ]
+
+    @property
+    def slug(self) -> str:
+        return slugify(self.text)
+
+    def __str__(self) -> str:
+        return self.text
+
+
+class PersonQuestionChoice(models.Model):
+    """
+    Allowed answer to a :class:`PersonQuestion`.
+    """
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(fields=['question', 'text'],
+                                    name='unique_question_answer')
+        ]
+        ordering = [
+            'question__order',
+            'order',
+            'text',
+        ]
+
+    #: Question to which this answer belongs
+    question = models.ForeignKey(PersonQuestion, related_name='answers',
+                                 on_delete=models.CASCADE,
+                                 blank=False, null=False)
+
+    #: Text of answer
+    text = models.CharField(max_length=255,
+                            blank=False, null=False)
+
+    #: Position of this answer in the list
+    order = models.SmallIntegerField(default=0,
+                                     blank=False, null=False)
+
+    @property
+    def slug(self) -> str:
+        return slugify(self.text)
+
+    def __str__(self) -> str:
+        return self.text
+
+
 class Person(models.Model):
     """
     A person may be a member of the BRECcIA core team or an external stakeholder.
@@ -168,13 +235,6 @@ class Person(models.Model):
     #: Discipline(s) within which this person works
     disciplines = models.CharField(max_length=255, blank=True, null=True)
 
-    #: Role this person holds within the project
-    role = models.ForeignKey(Role,
-                             on_delete=models.PROTECT,
-                             related_name='holders',
-                             blank=True,
-                             null=True)
-
     #: Project themes within this person works
     themes = models.ManyToManyField(Theme, related_name='people', blank=True)
 
@@ -183,8 +243,42 @@ class Person(models.Model):
         return self.relationships_as_source.all().union(
             self.relationships_as_target.all())
 
+    @property
+    def current_answers(self) -> 'PersonAnswerSet':
+        return self.answer_sets.last()
+
     def get_absolute_url(self):
         return reverse('people:person.detail', kwargs={'pk': self.pk})
 
     def __str__(self) -> str:
         return self.name
+
+
+class PersonAnswerSet(models.Model):
+    """
+    The answers to the person questions at a particular point in time.
+    """
+
+    class Meta:
+        ordering = [
+            'timestamp',
+        ]
+
+    #: Person to which this answer set belongs
+    person = models.ForeignKey(Person,
+                               on_delete=models.CASCADE,
+                               related_name='answer_sets',
+                               blank=False, null=False)
+
+    #: Answers to :class:`PersonQuestion`s
+    question_answers = models.ManyToManyField(PersonQuestionChoice)
+
+    #: When were these answers collected?
+    timestamp = models.DateTimeField(auto_now_add=True,
+                                     editable=False)
+
+    replaced_timestamp = models.DateTimeField(blank=True, null=True,
+                                              editable=False)
+
+    def get_absolute_url(self):
+        return self.person.get_absolute_url()