docs(postgres): init; specify unix-domain socket length limitation (#147)

Co-authored-by: Sridhar Ratnakumar <3998+srid@users.noreply.github.com>

doc/postgresql.md

@@ -0,0 +1,35 @@
+# PostgreSQL
+
+[PostgreSQL](https://www.postgresql.org/) is a powerful, open source object-relational database system with over 35 years of active development that has earned it a strong reputation for reliability, feature robustness, and performance.
+
+## Getting Started
+
+```nix
+# In `perSystem.process-compose.<name>`
+{
+  services.postgres."pg1".enable = true;
+}
+```
+
+## Examples
+
+- Run postgres server initialised with a sample database and graphically interact with it using [pgweb](https://github.com/sosedoff/pgweb): <https://github.com/juspay/services-flake/tree/main/example/simple>
+
+## Gotchas
+
+{#socket-path}
+### Unix-domain socket path is too long
+
+We already talk about this in the [data directory guide](guide/datadir.md#socket-path). In case of postgres, you can set `socketDir` while keeping the `dataDir` unchanged.
+
+>[!note]
+> The `socketDir` must be set to a shorter path (less than 100 chars) as a workaround.
+
+```nix
+{
+  services.postgres."pg1" = {
+    enable = true;
+    socketDir = "/tmp/pg1";
+  };
+}
+```

doc/services.md

@@ -12,7 +12,7 @@ short-title: Services
 - Elasticsearch
 - MySQL
 - Nginx
-- PostgreSQL
+- [[postgresql]]#
 - Redis
 - Redis Cluster
 - Zookeeper