Add external payload stats to WorkflowExecutionInfo (#689)

_**READ BEFORE MERGING:** All PRs require approval by both Server AND
SDK teams before merging! This is why the number of required approvals
is "2" and not "1"--two reviewers from the same team is NOT sufficient.
If your PR is not approved by someone in BOTH teams, it may be summarily
reverted._

<!-- Describe what has changed in this PR -->
Added external payload size and count to WorkflowExecutionInfo

<!-- Tell your future self why have you made these changes -->
We would like to show external payload stats for workflow execution.
That's why we are adding it to WorkflowExecutionInfo, so that Temporal
UI can call DescribeWorkflowExecution and use the result to show the
total external payload size and count for the workflow execution.

<!-- Are there any breaking changes on binary or code level? -->
No


<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
N/A

Author: simvlad

openapi/openapiv2.json

@@ -17001,6 +17001,16 @@
         "priority": {
           "$ref": "#/definitions/v1Priority",
           "title": "Priority metadata"
+        },
+        "externalPayloadSizeBytes": {
+          "type": "string",
+          "format": "int64",
+          "description": "Total size in bytes of all external payloads referenced in workflow history."
+        },
+        "externalPayloadCount": {
+          "type": "string",
+          "format": "int64",
+          "description": "Count of external payloads referenced in workflow history."
         }
       },
       "description": "Hold basic information about a workflow execution.\nThis structure is a part of visibility, and thus contain a limited subset of information."

openapi/openapiv3.yaml

@@ -14474,6 +14474,12 @@ components:
           allOf:
             - $ref: '#/components/schemas/Priority'
           description: Priority metadata
+        externalPayloadSizeBytes:
+          type: string
+          description: Total size in bytes of all external payloads referenced in workflow history.
+        externalPayloadCount:
+          type: string
+          description: Count of external payloads referenced in workflow history.
       description: |-
         Hold basic information about a workflow execution.
          This structure is a part of visibility, and thus contain a limited subset of information.

temporal/api/workflow/v1/message.proto

@@ -98,6 +98,12 @@ message WorkflowExecutionInfo {
 
     // Priority metadata
     temporal.api.common.v1.Priority priority = 24;
+
+    // Total size in bytes of all external payloads referenced in workflow history.
+    int64 external_payload_size_bytes = 25;
+
+    // Count of external payloads referenced in workflow history.
+    int64 external_payload_count = 26;
 }
 
 // Holds all the extra information about workflow execution that is not part of Visibility.