create new mosaic associations meta block

there seems to be issues with tag definitions which is currently not understood.

src/rad/resources/manifests/datamodels-1.0.yaml

@@ -135,6 +135,11 @@ tags:
   title: Basic mosaic metadata keywords
   description: |-
     Basic mosaic metadata keywords
+- tag_uri: asdf://stsci.edu/datamodels/roman/tags/mosaic_associations-1.0.0
+  schema_uri: asdf://stsci.edu/datamodels/roman/schemas/mosaic_associations-1.0.0
+  title: Mosaic associations metadata keywords
+  description: |-
+    Mosaic associations metadata keywords
 - tag_uri: asdf://stsci.edu/datamodels/roman/tags/mosaic_wcsinfo-1.0.0
   schema_uri: asdf://stsci.edu/datamodels/roman/schemas/mosaic_wcsinfo-1.0.0
   title: Mosaic WCS parameters

src/rad/resources/schemas/mosaic_associations-1.0.0.yaml

@@ -0,0 +1,18 @@
+%YAML 1.1
+---
+$schema: asdf://stsci.edu/datamodels/roman/schemas/rad_schema-1.0.0
+id: asdf://stsci.edu/datamodels/roman/schemas/mosaic_associations-1.0.0
+
+title: Association information for mosaic
+
+type: object
+properties:
+  pool_name:
+    type: string
+  table_name:
+    type: string
+
+required: [pool_name, table_name]
+flowStyle: block
+propertyOrder: [pool_name, table_name]
+...

src/rad/resources/schemas/wfi_mosaic-1.0.0.yaml

@@ -15,10 +15,9 @@ properties:
     allOf:
       - type: object
         properties:
-          # Placeholder for 'asn' schema tag
           # Placeholder for 'dither' schema tag
-          # asn:
-          #   tag: asdf://stsci.edu/datamodels/roman/tags/associations-1.0.0
+          asn:
+            tag: asdf://stsci.edu/datamodels/roman/tags/mosaic_associations-1.0.0
           basic:
             tag: asdf://stsci.edu/datamodels/roman/tags/mosaic_basic-1.0.0
           cal_step: