fix init_db.sql to also take variables from environment (#556)

* fix init_db.sql to also take variables from environment

* make other occurrences of username dynamic

* Update docker/init_db.sql

Co-authored-by: Lari Hotari <lhotari@users.noreply.github.com>

Author: Mortom123

docker/init_db.sql

@@ -12,9 +12,12 @@
 -- limitations under the License.
 --
 
-ALTER USER pulsar WITH PASSWORD 'pulsar';
-CREATE DATABASE pulsar_manager OWNER pulsar;
-GRANT ALL PRIVILEGES ON DATABASE pulsar_manager to pulsar;
+\set username `echo "${USERNAME:-pulsar}"`
+\set password `echo "${PASSWORD:-pulsar}"`
+
+ALTER USER :username WITH PASSWORD :'password';
+CREATE DATABASE pulsar_manager OWNER :username;
+GRANT ALL PRIVILEGES ON DATABASE pulsar_manager to :username;
 
 \c pulsar_manager;