refactor(people): Move relationship answers to answer set

Answers to the relationship questions have been moved from the relationship
to another model RelationshipAnswerSet.  A new answer set is created each
time a user answers the relationship questions.

Resolves #16
Resolves #17
Resolves #18

people/models/person.py

@@ -0,0 +1,186 @@
+import typing
+
+from django.conf import settings
+from django.contrib.auth.models import AbstractUser
+from django.db import models
+from django.urls import reverse
+from django.utils.translation import gettext_lazy as _
+
+from django_countries.fields import CountryField
+
+from backports.db.models.enums import TextChoices
+
+__all__ = [
+    'User',
+    'Organisation',
+    'Role',
+    'Discipline',
+    'Theme',
+    'Person',
+]
+
+
+class User(AbstractUser):
+    """
+    Custom user model in case we need to make changes later.
+    """
+    def has_person(self) -> bool:
+        """
+        Does this user have a linked :class:`Person` record?
+        """
+        try:
+            person = self.person
+            return True
+
+        except AttributeError:
+            return False
+
+
+class Organisation(models.Model):
+    """
+    Organisation to which a :class:`Person` belongs.
+    """
+    name = models.CharField(max_length=255,
+                            blank=False, null=False)
+    
+    def __str__(self) -> str:
+        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 Discipline(models.Model):
+    """
+    Discipline within which a :class:`Person` works.
+    """
+    name = models.CharField(max_length=255,
+                            blank=False, null=False)
+
+    #: Short code using system such as JACS 3
+    code = models.CharField(max_length=15,
+                            blank=True, null=False)
+
+    def __str__(self) -> str:
+        return self.name
+    
+    
+class Theme(models.Model):
+    """
+    Project theme within which a :class:`Person` works.
+    """
+    name = models.CharField(max_length=255,
+                            blank=False, null=False)
+
+    def __str__(self) -> str:
+        return self.name
+
+
+class Person(models.Model):
+    """
+    A person may be a member of the BRECcIA core team or an external stakeholder.
+    """
+    class Meta:
+        verbose_name_plural = 'people'
+
+    #: User account belonging to this person
+    user = models.OneToOneField(settings.AUTH_USER_MODEL,
+                                related_name='person',
+                                on_delete=models.CASCADE,
+                                blank=True, null=True)
+
+    #: Name of the person
+    name = models.CharField(max_length=255,
+                            blank=False, null=False)
+
+    #: Is this person a member of the core project team?
+    core_member = models.BooleanField(default=False,
+                                      blank=False, null=False)
+
+    #: People with whom this person has relationship - via intermediate :class:`Relationship` model
+    relationship_targets = models.ManyToManyField('self', related_name='relationship_sources',
+                                                  through='Relationship',
+                                                  through_fields=('source', 'target'),
+                                                  symmetrical=False)
+
+    ###############################################################
+    # Data collected for analysis of community makeup and structure
+
+    class GenderChoices(TextChoices):
+        MALE = 'M', _('Male')
+        FEMALE = 'F', _('Female')
+        OTHER = 'O', _('Other')
+        PREFER_NOT_TO_SAY = 'N', _('Prefer not to say')
+
+    gender = models.CharField(max_length=1,
+                              choices=GenderChoices.choices,
+                              blank=True, null=False)
+
+    class AgeGroupChoices(TextChoices):
+        LTE_25 = '<=25', _('25 or under')
+        BETWEEN_26_30 = '26-30', _('26-30')
+        BETWEEN_31_35 = '31-35', _('31-35')
+        BETWEEN_36_40 = '36-40', _('36-40')
+        BETWEEN_41_45 = '41-45', _('41-45')
+        BETWEEN_46_50 = '46-50', _('46-50')
+        BETWEEN_51_55 = '51-55', _('51-55')
+        BETWEEN_56_60 = '56-60', _('56-60')
+        GTE_61 = '>=61', _('61 or older')
+        PREFER_NOT_TO_SAY = 'N', _('Prefer not to say')
+
+    age_group = models.CharField(max_length=5,
+                                 choices=AgeGroupChoices.choices,
+                                 blank=True, null=False)
+    
+    nationality = CountryField(blank=True, null=True)
+
+    country_of_residence = CountryField(blank=True, null=True)
+
+    #: Organisation this person is employed by or affiliated with
+    organisation = models.ForeignKey(Organisation,
+                                     on_delete=models.PROTECT,
+                                     related_name='members',
+                                     blank=True, null=True)
+
+    #: Job title this person holds within their organisation
+    job_title = models.CharField(max_length=255,
+                                 blank=True, null=False)
+
+    #: Discipline within which this person works
+    discipline = models.ForeignKey(Discipline,
+                                   on_delete=models.PROTECT,
+                                   related_name='people',
+                                   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)
+
+    @property
+    def relationships(self):
+        return self.relationships_as_source.all().union(
+            self.relationships_as_target.all()
+        )
+
+    def get_absolute_url(self):
+        return reverse('people:person.detail', kwargs={'pk': self.pk})
+
+    def __str__(self) -> str:
+        return self.name
+
+