Using jsonschema for create_template.

Updated jsonschema to Draft7, this allowed a conditional validation on subject, if template_type == 'email' or 'letter' then subject is required.
This version is backward compatible with Draft4.
When creating TempalteRedacted, I've built the dict depending on if the created_by or created_by_id exists.

app/template/template_schemas.py

@@ -0,0 +1,28 @@
+from app.models import (
+    TEMPLATE_PROCESS_TYPE,
+    TEMPLATE_TYPES,
+)
+from app.schema_validation.definitions import uuid
+
+post_create_template_schema = {
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "description": "POST create new template",
+    "type": "object",
+    "title": "payload for POST /service/<uuid:service_id>/template",
+    "properties": {
+        "name": {"type": "string"},
+        "template_type": {"enum": TEMPLATE_TYPES},
+        "service": uuid,
+        "process_type": {"emun": TEMPLATE_PROCESS_TYPE},
+        "content": {"type": "string"},
+        "subject": {"type": "string"},
+        "created_by": uuid
+    },
+    "if": {
+        "properties": {
+            "template_type": {"enum": ["email", "letter"]}
+        }
+    },
+    "then": {"required": ["subject"]},
+    "required": ["name", "template_type", "content", "service", "created_by"]
+}