Merge pull request #4147 from SDA-SE/feat/origin-location

Block the deletion of entities from the bootstrap location in the unregister dialog and list the correct delete preview

docs/features/software-catalog/well-known-annotations.md

@@ -22,7 +22,7 @@ use.
 # Example:
 metadata:
   annotations:
-    backstage.io/managed-by-location: github:http://github.com/backstage/backstage/catalog-info.yaml
+    backstage.io/managed-by-location: url:http://github.com/backstage/backstage/catalog-info.yaml
 ```
 
 The value of this annotation is a so called location reference string, that
@@ -30,8 +30,8 @@ points to the source from which the entity was originally fetched. This
 annotation is added automatically by the catalog as it fetches the data from a
 registered location, and is not meant to normally be written by humans. The
 annotation may point to any type of generic location that the catalog supports,
-so it cannot be relied on to always be specifically of type `github`, nor that
-it even represents a single file. Note also that a single location can be the
+so it cannot be relied on to always be specifically of type `url`, nor that it
+even represents a single file. Note also that a single location can be the
 source of many entities, so it represents a many-to-one relationship.
 
 The format of the value is `<type>:<target>`. Note that the target may also
@@ -40,13 +40,30 @@ expecting a two-item array out of it. The format of the target part is
 type-dependent and could conceivably even be an empty string, but the separator
 colon is always present.
 
+### backstage.io/managed-by-origin-location
+
+```yaml
+# Example:
+metadata:
+  annotations:
+    backstage.io/managed-by-origin-location: url:http://github.com/backstage/backstage/catalog-info.yaml
+```
+
+The value of this annotation is a location reference string (see above). It
+points to the location, whose registration lead to the creation of the entity.
+In most cases, the `backstage.io/managed-by-location` and
+`backstage.io/managed-by-origin-location` will be equal. They will be different
+if the original location delegates to another location. A common case is, that a
+location is registered as `bootstrap:boostrap` which means that it is part of
+the `app-config.yaml` of a Backstage installation.
+
 ### backstage.io/techdocs-ref
 
 ```yaml
 # Example:
 metadata:
   annotations:
-    backstage.io/techdocs-ref: github:https://github.com/backstage/backstage.git
+    backstage.io/techdocs-ref: url:https://github.com/backstage/backstage.git
 ```
 
 The value of this annotation is a location reference string (see above). If this