Deprecate v0 series

Author: sethvargo

src/main.ts

@@ -50,6 +50,17 @@ enum ResponseTypes {
  * primary entry point. It is documented inline.
  */
 export async function run(): Promise<void> {
+  // v0 is deprecated and is no longer supported per our "two major versions"
+  // policy.
+  core.error(
+    `The v0 series of google-github-actions/deploy-cloudrun is no longer ` +
+      `maintained. It will not receive updates, improvements, or security ` +
+      `patches. Please upgrade to the latest supported versions: ` +
+      `\n` +
+      `\n` +
+      `    https://github.com/google-github-actions/deploy-cloudrun`,
+  );
+
   core.exportVariable(GCLOUD_METRICS_ENV_VAR, GCLOUD_METRICS_LABEL);
   try {
     // Get inputs