Add documents to decoders (#22)

* Add decoder documents support
* Use abstract model for Documents
* Increase version
* Code cleanup

ram/metadata/models.py

@@ -1,11 +1,10 @@
-from urllib.parse import quote
-
 from django.db import models
 from django.urls import reverse
 from django.conf import settings
 from django.dispatch.dispatcher import receiver
 from django_countries.fields import CountryField
 
+from ram.models import Document
 from ram.utils import DeduplicatedStorage, get_image_preview, slugify
 
 
@@ -88,7 +87,7 @@ class Decoder(models.Model):
     manufacturer = models.ForeignKey(
         Manufacturer,
         on_delete=models.CASCADE,
-        limit_choices_to={"category": "model"},
+        limit_choices_to={"category": "accessory"},
     )
     version = models.CharField(max_length=64, blank=True)
     sound = models.BooleanField(default=False)
@@ -105,6 +104,15 @@ class Decoder(models.Model):
     image_thumbnail.short_description = "Preview"
 
 
+class DecoderDocument(Document):
+    decoder = models.ForeignKey(
+        Decoder, on_delete=models.CASCADE, related_name="document"
+    )
+
+    class Meta:
+        unique_together = ("decoder", "file")
+
+
 class Scale(models.Model):
     scale = models.CharField(max_length=32, unique=True)
     slug = models.CharField(max_length=32, unique=True, editable=False)
@@ -167,7 +175,6 @@ class Tag(models.Model):
         )
 
 
-
 @receiver(models.signals.pre_save, sender=Manufacturer)
 @receiver(models.signals.pre_save, sender=Company)
 @receiver(models.signals.pre_save, sender=Scale)