old_contents: from django.db.models import ForeignKey, DateTimeField
  from yunity.models.entities import User, Location, Mappable, Contact
  from yunity.models.utils import BaseModel, MaxLengthCharField
  from yunity.utils.decorators import classproperty
  
  
  class MappableLocation(BaseModel):
      mappable = ForeignKey(Mappable)
      location = ForeignKey(Location)
      startTime = DateTimeField(null=True)
      endTime = DateTimeField(null=True)
  
  
  class MappableResponsibility(BaseModel):
      @classproperty
      def TYPE(cls):
          return cls.create_constants('type', 'OWNER')
  
      responsible = ForeignKey(User)
      mappable = ForeignKey(Mappable)
      status = MaxLengthCharField()
      date = DateTimeField(null=True)
      type = MaxLengthCharField()
  
  
  class UserLocation(BaseModel):
      user = ForeignKey(User)
      location = ForeignKey(Location)
      type = MaxLengthCharField()
  
  
  class ItemRequest(BaseModel):
      requester = ForeignKey(User)
      requested = ForeignKey(Mappable)
      feedback = MaxLengthCharField(null=True, default=None)
  
  
new_contents: from django.db.models import ForeignKey, DateTimeField, ManyToManyField
  from yunity.models.entities import User, Location, Mappable, Contact, Message
  from yunity.models.utils import BaseModel, MaxLengthCharField
  from yunity.utils.decorators import classproperty
  
  
  class Chat(BaseModel):
      participants = ManyToManyField(User)
      messages = ManyToManyField(Message)
  
  
  class MappableLocation(BaseModel):
      mappable = ForeignKey(Mappable)
      location = ForeignKey(Location)
      startTime = DateTimeField(null=True)
      endTime = DateTimeField(null=True)
  
  
  class MappableResponsibility(BaseModel):
      @classproperty
      def TYPE(cls):
          return cls.create_constants('type', 'OWNER')
  
      responsible = ForeignKey(User)
      mappable = ForeignKey(Mappable)
      status = MaxLengthCharField()
      date = DateTimeField(null=True)
      type = MaxLengthCharField()
  
  
  class UserLocation(BaseModel):
      user = ForeignKey(User)
      location = ForeignKey(Location)
      type = MaxLengthCharField()
  
  
  class ItemRequest(BaseModel):
      requester = ForeignKey(User)
      requested = ForeignKey(Mappable)
      feedback = MaxLengthCharField(null=True, default=None)
  
  
subject: Add Chat relation