Added description schema

storage_service/schemas/__init__.py

@@ -1 +1,2 @@
 #!/usr/bin/env python3
+from .description_schema import DescriptionSchema

storage_service/schemas/description_schema.py

@@ -0,0 +1,9 @@
+from marshmallow import Schema, fields, RAISE
+from marshmallow.validate import Regexp, Length
+
+
+class DescriptionSchema(Schema):
+    tag = fields.Str(required=True, validate=[Regexp("^[a-zA-Z]+[0-9a-zA-Z_]*$"), Length(min=2, max=32)])
+
+    class Meta:
+        unknown = RAISE  # Later this could be changed to EXCLUDE to maintain compatibility among versions