Create vagrant postgres user and grant it rights to zulip{,_test}

(imported from commit bb57a3f5ef8bc48553f1eff95c47894aed4ef975)

tools/postgres-init-db

@@ -7,6 +7,8 @@ if [ "$(uname)" = "Darwin" ]; then
    DEFAULT_DB="postgres"
 fi
 
+VAGRANTUSERNAME=$(whoami)
+
 if [[ $# == 0 ]]; then
     USERNAME=zulip
     PASSWORD=$($(dirname $0)/../bin/get-django-setting LOCAL_DATABASE_PASSWORD)
@@ -30,6 +32,19 @@ $ROOT_POSTGRES $DEFAULT_DB << EOF
 CREATE USER $USERNAME WITH PASSWORD '$PASSWORD';
 ALTER USER $USERNAME CREATEDB;
 ALTER ROLE $USERNAME SET search_path TO $SEARCH_PATH;
+
+DO \$\$
+  BEGIN
+    IF NOT EXISTS (
+      SELECT * FROM pg_catalog.pg_user WHERE usename -- [sic]
+          = '$VAGRANTUSERNAME') THEN
+
+      CREATE USER $VAGRANTUSERNAME;
+    END IF;
+  END
+\$\$ ;
+GRANT $USERNAME TO $VAGRANTUSERNAME;
+ALTER ROLE $VAGRANTUSERNAME SET search_path TO $SEARCH_PATH;
 EOF
 
 umask go-rw