[TC-642] modify template (#3)

https://eva.avroid.tech/desk/Task/TC-642#be-dorabotat-shablon-servisov-backend

Дорабатываем шаблон сервисов по требованиям: https://eva.avroid.tech/project/Document/DOC-002710#trebovanija-k-versijam

Reviewed-on: https://git.avroid.tech/Templates/template-backend-service/pulls/3
Reviewed-by: Victor Stratov <victor.stratov@avroid.team>
Reviewed-by: Petr Brovchenko <petr.brovchenko@avroid.team>
Co-authored-by: Nadezhda <nadezhda.lavrentieva@avroid.team>
Co-committed-by: Nadezhda <nadezhda.lavrentieva@avroid.team>

local.env.example

@@ -1,13 +1,2 @@
-POSTGRES_USER=test
-POSTGRES_PASSWORD=test
-POSTGRES_HOST=cloud-postgres.avroid.cloud
-POSTGRES_DB=messenger
-POSTGRES_PORT=5432
-
-SCYLLADB_HOST=cloud-scylla.avroid.cloud
-SCYLLADB_PORT=9042
-SCYLLADB_USER=test
-SCYLLADB_PASSWORD=test
-SCYLLADB_KEYSPACE=messenger
-
+POSTGRES_DSN=postgresql://postgres_user:postgres_password@postgres_host:5432/db
 PORT=8000