add: postgres version requirement (#4611)

docs/admin/configure.md

@@ -29,6 +29,8 @@ Coder uses a PostgreSQL database to store users, workspace metadata, and other d
 Use `CODER_PG_CONNECTION_URL` to set the database that Coder connects to. If unset, PostgreSQL binaries will be
 downloaded from Maven (https://repo1.maven.org/maven2) and store all data in the config root.
 
+> Postgres 13 is the minimum supported version.
+
 ## System packages
 
 If you've installed Coder via a [system package](../install/packages.md) Coder, you can

docs/install/binary.md

@@ -17,7 +17,7 @@ Coder publishes self-contained .zip and .tar.gz archives in [GitHub releases](ht
    # Automatically sets up an external access URL on *.try.coder.app
    coder server
 
-   # Requires a PostgreSQL instance and external access URL
+   # Requires a PostgreSQL instance (version 13 or higher) and external access URL
    coder server --postgres-url <url> --access-url <url>
    ```
 

docs/install/docker.md

@@ -30,9 +30,9 @@ Learn more about Coder's [configuration options](../admin/configure.md).
 
 ## Run Coder with access URL and external PostgreSQL (recommended)
 
-For production deployments, we recommend using an external PostgreSQL database.
-Set `ACCESS_URL` to the external URL that users and workspaces will use to
-connect to Coder.
+For production deployments, we recommend using an external PostgreSQL database
+(version 13 or higher). Set `ACCESS_URL` to the external URL that users and
+workspaces will use to connect to Coder.
 
 ```sh
 docker run --rm -it \