Core Module readme

Lambdas/Lists/src/README.md

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+# Core Module
+Wraps inner business functionality and abstracts certain environment interactions such as opening/closing the database connection and processing the API Gateway input json.
+
+#### Expected input json:
+The following is created by APIGateway along the lines of [this](https://github.com/ClaytonWWilson/Listify/blob/master/Tooling/body_and_auth_mapping.json) definition
+```
+{
+  "body": {jsonizedPOSTEDObject},
+  "params": {
+      "querystring": {
+          "queryParamifApplicable": "paramValue"
+      }
+   },
+   "context": {
+       "sub": "cognitoID"
+   }
+}
+```
+
+`querystring` will only have subcomponents if there are query parameters
+
+
+`{jsonizedPOSTEDObject}` will be something like:
+```
+{
+    "var1": 1,
+    "var2": "string"
+}
+```
+
+#### Module Contract:
+For the module contract see [CallHandler](https://github.com/ClaytonWWilson/Listify/blob/master/Lambdas/Lists/src/main/java/CallHandler.java)
+
+#### Returns
+Business logic return or error is appropriate
+