chore(ci): Add downstream merge trigger to github action (#3014)

scripts/trigger-merge-to-downstream-gha

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+
+BRANCH=${1}
+
+if [[ -z "${BRANCH}" ]]; then
+    echo "skipping no branch specified"
+    exit 0
+fi
+
+if [[ -z "${DOWNSTREAM_SLUG}" ]]; then
+    echo "skipping, no downstream"
+    exit 0
+fi
+
+if [[ -z ${DOWNSTREAM_TOK} ]]; then
+  exit 0
+fi
+
+if [[ -z ${DOWNSTREAM_WORKFLOW} ]]; then
+    echo "skipping, no downstream workflow"
+    exit 0
+fi
+
+curl \
+  --silent \
+  -X POST \
+  -H "Accept: application/vnd.github+json" \
+  -H "Authorization: Bearer ${DOWNSTREAM_TOK}" \
+  -H "X-GitHub-Api-Version: 2022-11-28" \
+  "https://api.github.com/repos/hashicorp/boundary-${DOWNSTREAM_SLUG}/actions/workflows/${DOWNSTREAM_WORKFLOW}/dispatches" \
+  -d @- << EOF
+{
+  "ref": "${BRANCH}",
+  "inputs": {
+    "from-branch": "${BRANCH}",
+    "to-branch": "${BRANCH}"
+  }
+}
+EOF