feat(core): add model tag to manufacturer

ref: #807 #796

app/core/models/manufacturer.py

@@ -12,6 +12,8 @@ class Manufacturer(
     CenturionModel,
 ):
 
+    model_tag = 'manufacturer'
+
 
     class Meta:
 

docs/projects/centurion_erp/user/core/markdown.md

@@ -87,8 +87,8 @@ A Model link is a reference to an item within the database. Supported model link
 | group| `$-<id>` |
 | it_asset | `$it_asset-<id>` |
 | knowledgebase| `$kb-<id>` |
-| knowledgebasecategory| `$-<id>` |
-| manufacturer| `$-<id>` |
+| knowledgebasecategory| `$kb_category-<id>` |
+| manufacturer| `$manufacturer-<id>` |
 | modelnotes| `$-<id>` |
 | operatingsystem| `$operating_system-<id>` |
 | operatingsystemversion| `$-<id>` |