Add the Synapse signing key generator

scripts/gen_synapse_key.py

@@ -0,0 +1,15 @@
+import random
+import string
+import io
+from signedjson.key import generate_signing_key, write_signing_keys
+
+
+def random_string(length):
+    return ''.join(random.choice(string.ascii_letters) for _ in range(length))
+
+
+key_id = "a_" + random_string(4)
+with io.StringIO() as f:
+    write_signing_keys(f, (generate_signing_key(key_id),),)
+    f.seek(0)
+    print(f.read())