Fix: [AEA-4045] - PSU returning empty 200 response with header Conten…

…t-Type set to application/fhir+json (#276)

## Summary

🎫 [AEA-4045](https://nhsd-jira.digital.nhs.uk/browse/AEA-4045) PSU
returning empty 200 response with header Content-Type set to
application/fhir+json

- 🤖 Operational or Infrastructure Change

### Details

PSU returning empty 200 response with header Content-Type set to
application/fhir+json.

- Expected Behaviour
The response is processed successfully (data added to dynamodb if all
items pass validation)
A 201 response is returned if all items pass validation
A 400 response is returned if items fail validation

- Observed Behaviour
A 200 response is returned with 3 empty lines if validation passes or
fails

---------

Co-authored-by: Anthony Brown <[email protected]>

Makefile

@@ -84,7 +84,7 @@ sam-deploy-package: guard-artifact_bucket guard-artifact_bucket_prefix guard-sta
 			  TruststoreVersion=$$LATEST_TRUSTSTORE_VERSION \
 			  EnableMutualTLS=$$enable_mutual_tls \
 			  EnableSplunk=true \
-				EnableDynamoDBAutoScaling=$$DYNAMODB_AUTOSCALE \
+			  EnableDynamoDBAutoScaling=$$DYNAMODB_AUTOSCALE \
 			  VersionNumber=$$VERSION_NUMBER \
 			  CommitId=$$COMMIT_ID \
 			  LogLevel=$$LOG_LEVEL \

SAMtemplates/apis/main.yaml

@@ -198,6 +198,70 @@ Resources:
                   "input": "{$util.escapeJavaScript($inputString.substring(1,$len))}"
               }
             - stateMachineArn: !Ref UpdatePrescriptionStatusStateMachineArn
+          application/fhir+json: !Sub
+            - |-
+              ## Velocity Template used for API Gateway request mapping template
+              ## "@@" is used here as a placeholder for '"' to avoid using escape characters.
+
+              #set($includeHeaders = true)
+              #set($includeQueryString = true)
+              #set($includePath = true)
+              #set($requestContext = '')
+
+              #set($inputString = '')
+              #set($allParams = $input.params())
+              #set($allParams.header.apigw-request-id = $context.requestId)
+              {
+                  "stateMachineArn": "${stateMachineArn}",
+
+                  #set($inputString = "$inputString,@@body@@: $input.body")
+
+                  #if ($includeHeaders)
+                      #set($inputString = "$inputString, @@headers@@:{")
+                      #foreach($paramName in $allParams.header.keySet())
+                          #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.header.get($paramName))@@")
+                          #if($foreach.hasNext)
+                              #set($inputString = "$inputString,")
+                          #end
+                      #end
+                      #set($inputString = "$inputString }")
+
+                  #end
+
+                  #if ($includeQueryString)
+                      #set($inputString = "$inputString, @@querystring@@:{")
+                      #foreach($paramName in $allParams.querystring.keySet())
+                          #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.querystring.get($paramName))@@")
+                          #if($foreach.hasNext)
+                              #set($inputString = "$inputString,")
+                          #end
+                      #end
+                      #set($inputString = "$inputString }")
+                  #end
+
+                  #if ($includePath)
+                      #set($inputString = "$inputString, @@path@@:{")
+                      #foreach($paramName in $allParams.path.keySet())
+                          #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.path.get($paramName))@@")
+                          #if($foreach.hasNext)
+                              #set($inputString = "$inputString,")
+                          #end
+                      #end
+                      #set($inputString = "$inputString }")
+                  #end
+
+                  ## Check if the request context should be included as part of the execution input
+                  #if($requestContext && !$requestContext.empty)
+                      #set($inputString = "$inputString,")
+                      #set($inputString = "$inputString @@requestContext@@: $requestContext")
+                  #end
+
+                  #set($inputString = "$inputString}")
+                  #set($inputString = $inputString.replaceAll("@@",'"'))
+                  #set($len = $inputString.length() - 1)
+                  "input": "{$util.escapeJavaScript($inputString.substring(1,$len))}"
+              }
+            - stateMachineArn: !Ref UpdatePrescriptionStatusStateMachineArn
         IntegrationResponses:
           - StatusCode: 200
             ResponseTemplates:
@@ -214,9 +278,9 @@ Resources:
             ResponseTemplates:
               application/json: |-
                 #set($context.responseOverride.header["Content-Type"] ="application/fhir+json")
-                {"resourceType":"OperationOutcome","issue": [{"severity":"error","code":"processing","diagnostics":"System error"}]}    
+                {"resourceType":"OperationOutcome","issue": [{"severity":"error","code":"processing","diagnostics":"System error"}]}
           - StatusCode: 500
-            SelectionPattern: ^5\d{2}.* 
+            SelectionPattern: ^5\d{2}.*
             ResponseTemplates:
               application/json: |-
                 #set($context.responseOverride.header["Content-Type"] ="application/fhir+json")