Feature: Add customisable icons in topology (#193)

* [up] add config for custom images, better js

* [up] use bundler to bundle js

* [fix] remove domcontentloaded since defer is used

* [fix] formatting with black

* [fix] images drf api

* [up] add support for custom icons on additional roles: power panel, power feed, circuit

* [up] optimize topology generation by using `_id` when trying to access pk of related object

* [fix] kebab case instead of slugification

* [fix] use empty queryset in api views & change coord save logic

netbox_topology_views/models.py

@@ -0,0 +1,93 @@
+from pathlib import Path
+from typing import Optional
+
+from dcim.models import DeviceRole
+from django.conf import settings
+from django.contrib.contenttypes.models import ContentType
+from django.db import models
+from django.templatetags.static import static
+from netbox.models.features import (
+    ChangeLoggingMixin,
+    ExportTemplatesMixin,
+    WebhooksMixin,
+)
+
+from netbox_topology_views.utils import (
+    CONF_IMAGE_DIR,
+    IMAGE_DIR,
+    Role,
+    find_image_url,
+    get_model_role,
+    image_static_url,
+)
+
+
+class RoleImage(ChangeLoggingMixin, ExportTemplatesMixin, WebhooksMixin):
+    class Meta:
+        indexes = [
+            models.Index(fields=["content_type", "object_id"]),
+        ]
+
+    objects: "models.Manager[RoleImage]"
+
+    image = models.CharField("Path within the netbox static directory", max_length=255)
+
+    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    object_id = models.PositiveIntegerField(null=True, blank=True)
+
+    __role: Optional[Role] = None
+
+    @property
+    def role(self) -> Role:
+        if self.__role:
+            return self.__role
+
+        model_class = self.content_type.model_class()
+
+        if not model_class:
+            raise ValueError(f"Invalid content type: {self.content_type}")
+
+        if model_class == DeviceRole:
+            device_role: DeviceRole = DeviceRole.objects.get(pk=self.object_id)
+            self.__role = Role(slug=device_role.slug, name=device_role.name)
+            return self.__role
+
+        self.__role = get_model_role(model_class)
+        return self.__role
+
+    def __str__(self):
+        return f"{self.role} - {self.image}"
+
+    def get_image(self) -> Path:
+        """Get Icon
+
+        returns the model's image's absolute path in the filesystem
+        raises ValueError if the file cannot be found
+        """
+        path = Path(settings.STATIC_ROOT) / self.image
+
+        if not path.exists():
+            raise ValueError(f"{self.role} path '{path}' does not exists")
+
+        return path
+
+    def get_default_image(self, dir: Path = CONF_IMAGE_DIR):
+        """Get default image
+
+        will attempt to find image in given directory with any file extension,
+        otherwise will try to find a `role-unknown` image
+
+        fallback is `STATIC_ROOT/netbox_topology_views/img/role-unknown.png`
+        """
+        if url := find_image_url(self.role.slug, dir):
+            return url
+
+        # fallback to default role unknown image
+        return image_static_url(IMAGE_DIR / "role-unknown.png")
+
+    def get_image_url(self, dir: Path = CONF_IMAGE_DIR) -> str:
+        try:
+            self.get_image()
+        except ValueError:
+            return self.get_default_image(dir)
+        return static(f"/{self.image}")