Add yaml error definition

schemas/CMakeLists.txt

@@ -4,5 +4,6 @@ install(
         config.yaml
         manifest.yaml
         type.yaml
+        error.yaml
     DESTINATION "${CMAKE_INSTALL_DATADIR}/everest/schemas"
 )

schemas/error.yaml

@@ -0,0 +1,40 @@
+$schema: http://json-schema.org/draft-07/schema#
+description: Json schema for EVerest error definition files
+$defs:
+  error_list_subschema:
+    allOf:
+      - $ref: http://json-schema.org/draft-07/schema#
+      - type: object
+        # require at least a type declaration
+        required:
+          - name
+          - description
+        properties:
+          name:
+            type: string
+            minLength: 2
+          description:
+            type: string
+            minLength: 2
+        # allow all sorts of entries (should be a json schema!)
+        additionalProperties: true
+type: object
+required:
+  - description
+properties:
+  description:
+    type: string
+    minLength: 2
+  errors:
+    description: This describes a list of errors of this unit
+    type: array
+    patternProperties:
+      # arbitrary type name
+      ^[a-zA-Z_][a-zA-Z0-9_.-]*$:
+        description: json schema declaring the error
+        $ref: '#/$defs/error_list_subschema'
+    # don't allow arbitrary additional properties
+    additionalProperties: false
+    # add empty types if not already present
+    default: {}
+additionalProperties: false