feat(cost): add GetInvoiceReadiness RPC for billing readiness check

cost/v1/cost.proto

@@ -582,6 +582,13 @@ service Cost {
     };
   }
 
+  // Synchronously checks billing readiness without triggering an export, email, or long-running operation.
+  rpc GetInvoiceReadiness(GetInvoiceReadinessRequest) returns (GetInvoiceReadinessResponse) {
+    option (google.api.http) = {
+      get: "/v1/{vendor}/reports/invoicereadiness"
+    };
+  }
+
   // Get the utilization details for an organization (or MSP).
   rpc GetUtilization(GetUtilizationRequest) returns (GetUtilizationResponse) {
     option (google.api.http) = {
@@ -1905,6 +1912,25 @@ message AwsExportReportOptions {
   map<string, Columns> columns_by_query = 5;
 }
 
+// Request message for GetInvoiceReadiness.
+message GetInvoiceReadinessRequest {
+  // Required. Bound from the URL path, so it cannot be empty/omitted.
+  // Accepted values: "aws", "gcp", "azure".
+  string vendor = 1;
+
+  // Required. Billing month in YYYY-MM format.
+  string month = 2 [(google.api.field_behavior) = REQUIRED];
+}
+
+// Response message for GetInvoiceReadiness.
+message GetInvoiceReadinessResponse {
+  // True if all usage for the requested month has an invoice ID (billing is finalized).
+  bool ready = 1;
+
+  // Human-readable explanation when ready is false. Empty when ready is true.
+  string reason = 2;
+}
+
 // Request message for GetUtilization
 message GetUtilizationRequest {
   // Required. At the moment, only `aws` is supported.

openapiv2/apidocs.swagger.json

@@ -21636,6 +21636,45 @@
         ]
       }
     },
+    "/v1/{vendor}/reports/invoicereadiness": {
+      "get": {
+        "summary": "Synchronously checks billing readiness without triggering an export, email, or long-running operation.",
+        "operationId": "Cost_GetInvoiceReadiness",
+        "responses": {
+          "200": {
+            "description": "A successful response.",
+            "schema": {
+              "$ref": "#/definitions/v1GetInvoiceReadinessResponse"
+            }
+          },
+          "default": {
+            "description": "An unexpected error response.",
+            "schema": {
+              "$ref": "#/definitions/rpcStatus"
+            }
+          }
+        },
+        "parameters": [
+          {
+            "name": "vendor",
+            "description": "Required. Bound from the URL path, so it cannot be empty/omitted.\nAccepted values: \"aws\", \"gcp\", \"azure\".",
+            "in": "path",
+            "required": true,
+            "type": "string"
+          },
+          {
+            "name": "month",
+            "description": "Required. Billing month in YYYY-MM format.",
+            "in": "query",
+            "required": true,
+            "type": "string"
+          }
+        ],
+        "tags": [
+          "Cost"
+        ]
+      }
+    },
     "/v1/{vendor}/services": {
       "get": {
         "summary": "Lists available cloud services and their associated SKUs for a given vendor.\nUse this to retrieve service codes and names that can be referenced in exclude service settings.",
@@ -41945,6 +41984,20 @@
       },
       "description": "Response message for GetInvoiceDisplaySettings rpc."
     },
+    "v1GetInvoiceReadinessResponse": {
+      "type": "object",
+      "properties": {
+        "ready": {
+          "type": "boolean",
+          "description": "True if all usage for the requested month has an invoice ID (billing is finalized)."
+        },
+        "reason": {
+          "type": "string",
+          "description": "Human-readable explanation when ready is false. Empty when ready is true."
+        }
+      },
+      "description": "Response message for GetInvoiceReadiness."
+    },
     "v1GetMSPDefaultMetaResponse": {
       "type": "object",
       "properties": {