feat(ssh-key): add generate-ssh-key script and update entrypoint for shallow clones and submodule depth

bin/generate-ssh-key

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+generate-ssh-key() {
+    echo 'Generate SSH private and public keys.'
+    mkdir -p tmp
+    if [[ ! -f "tmp/ed25519" ]]; then
+        ssh-keygen -t ed25519 -C admin@example.com -f tmp/ed25519 -N ''
+    fi
+    export GIT_SSH_PRIVATE_KEY=$(cat tmp/ed25519 | base64 -w0)
+    export GIT_SSH_PUBLIC_KEY=$(cat tmp/ed25519.pub)
+}