Simplify postgres setup

If POSTGRES_USER, POSTGRES_PASSWORD and POSTGRES_DB are set, the
postgres container automatically creates the database and role with the
set name and password.

configuration/postgresql/initdb/001-chirpstack_extensions.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname="chirpstack" <<-EOSQL
+psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname="$POSTGRES_DB" <<-EOSQL
     create extension pg_trgm;
     create extension hstore;
 EOSQL

configuration/postgresql/initdb/001-init-chirpstack.sh

@@ -1,7 +0,0 @@
-#!/bin/bash
-set -e
-
-psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" <<-EOSQL
-    create role chirpstack with login password 'chirpstack';
-    create database chirpstack with owner chirpstack;
-EOSQL

docker-compose.yml

@@ -60,7 +60,9 @@ services:
       - ./configuration/postgresql/initdb:/docker-entrypoint-initdb.d
       - postgresqldata:/var/lib/postgresql/data
     environment:
-      - POSTGRES_PASSWORD=root
+      - POSTGRES_USER=chirpstack
+      - POSTGRES_PASSWORD=chirpstack
+      - POSTGRES_DB=chirpstack
 
   redis:
     image: redis:7-alpine