Add LastCurrentTime to version info to tell if it ever became current (#692)

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<!-- Describe what has changed in this PR -->
**What changed?**
Add LastCurrentTime to version info to tell if it ever became current

<!-- Tell your future self why have you made these changes -->
**Why?**
So that the controller can accelerate rollout if it detects that the
target version was previously Current (aka it's actually a roll back)


<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**
None

<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
Doesn't break server, but here's the server PR:
temporalio/temporal#8845

Author: carlydf

openapi/openapiv2.json

@@ -8639,10 +8639,15 @@
           "format": "date-time",
           "description": "Timestamp when this version first became current or ramping."
         },
+        "lastCurrentTime": {
+          "type": "string",
+          "format": "date-time",
+          "description": "Timestamp when this version last became current.\nCan be used to determine whether a version has ever been Current."
+        },
         "lastDeactivationTime": {
           "type": "string",
           "format": "date-time",
-          "description": "Timestamp when this version last stopped being current or ramping."
+          "description": "Timestamp when this version last stopped being current or ramping.\nCleared if the version becomes current or ramping again."
         }
       }
     },
@@ -17541,10 +17546,15 @@
           "format": "date-time",
           "description": "Timestamp when this version first became current or ramping."
         },
+        "lastCurrentTime": {
+          "type": "string",
+          "format": "date-time",
+          "description": "Timestamp when this version last became current.\nCan be used to determine whether a version has ever been Current."
+        },
         "lastDeactivationTime": {
           "type": "string",
           "format": "date-time",
-          "description": "Timestamp when this version last stopped being current or ramping."
+          "description": "Timestamp when this version last stopped being current or ramping.\nCleared if the version becomes current or ramping again."
         },
         "rampPercentage": {
           "type": "number",

openapi/openapiv3.yaml

@@ -14738,9 +14738,17 @@ components:
           type: string
           description: Timestamp when this version first became current or ramping.
           format: date-time
+        lastCurrentTime:
+          type: string
+          description: |-
+            Timestamp when this version last became current.
+             Can be used to determine whether a version has ever been Current.
+          format: date-time
         lastDeactivationTime:
           type: string
-          description: Timestamp when this version last stopped being current or ramping.
+          description: |-
+            Timestamp when this version last stopped being current or ramping.
+             Cleared if the version becomes current or ramping again.
           format: date-time
     WorkerDeploymentOptions:
       type: object
@@ -14834,9 +14842,17 @@ components:
           type: string
           description: Timestamp when this version first became current or ramping.
           format: date-time
+        lastCurrentTime:
+          type: string
+          description: |-
+            Timestamp when this version last became current.
+             Can be used to determine whether a version has ever been Current.
+          format: date-time
         lastDeactivationTime:
           type: string
-          description: Timestamp when this version last stopped being current or ramping.
+          description: |-
+            Timestamp when this version last stopped being current or ramping.
+             Cleared if the version becomes current or ramping again.
           format: date-time
         rampPercentage:
           type: number

temporal/api/deployment/v1/message.proto

@@ -120,7 +120,13 @@ message WorkerDeploymentVersionInfo {
 
     // Timestamp when this version first became current or ramping.
     google.protobuf.Timestamp first_activation_time = 12;
+
+    // Timestamp when this version last became current.
+    // Can be used to determine whether a version has ever been Current.
+    google.protobuf.Timestamp last_current_time = 15;
+
     // Timestamp when this version last stopped being current or ramping.
+    // Cleared if the version becomes current or ramping again.
     google.protobuf.Timestamp last_deactivation_time = 13;
 
     // Range: [0, 100]. Must be zero if the version is not ramping (i.e. `ramping_since_time` is nil).
@@ -232,7 +238,11 @@ message WorkerDeploymentInfo {
         google.protobuf.Timestamp routing_update_time = 8;
         // Timestamp when this version first became current or ramping.
         google.protobuf.Timestamp first_activation_time = 9;
+        // Timestamp when this version last became current.
+        // Can be used to determine whether a version has ever been Current.
+        google.protobuf.Timestamp last_current_time = 12;
         // Timestamp when this version last stopped being current or ramping.
+        // Cleared if the version becomes current or ramping again.
         google.protobuf.Timestamp last_deactivation_time = 10;
     }
 }