[ADD] DO Documentation

docs/db_server.md

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+Either Use managed db service from DO https://www.digitalocean.com/products/managed-databases-postgresql 
+
+or Setup a new VPS and install Postgres on it as follows
+
+https://www.cherryservers.com/blog/how-to-install-and-setup-postgresql-server-on-ubuntu-20-04#step-6-setup-postgresql-server
+
+
+and dont forget to setup following
+
+
+    vim /etc/postgresql/14/main/postgresql.conf
+
+Uncomment and edit the listen_addresses attribute to start listening to start listening to all available IP addresses.
+
+    listen_addresses = '*'
+
+Now edit the PostgreSQL access policy configuration file.
+
+    vim /etc/postgresql/14/main/pg_hba.conf
+
+    Append a new connection policy (a pattern stands for [CONNECTION_TYPE][DATABASE][USER] [ADDRESS][METHOD]) in the bottom of the file.
+
+    host all all 0.0.0.0/0 md5
+
+We are allowing TCP/IP connections (host) to all databases (all) for all users (all) with any IPv4 address (0.0.0.0/0) using an MD5 encrypted password for authentication (md5).
+
+It is now time to restart your PostgreSQL service to load your configuration changes.
+
+    systemctl restart postgresql
+
+And make sure your system is listening to the 5432 port that is reserved for PostgreSQL.
+
+    ss -nlt | grep 5432
+