nix: Add postgrest-docs-render to render latex documents

nix/tools/docs.nix

@@ -2,8 +2,10 @@
 , aspellDicts
 , buildToolbox
 , checkedShellScript
+, imagemagick
 , python3
 , python3Packages
+, texlive
 , writers
 }:
 let
@@ -56,6 +58,19 @@ let
         fi
       '';
 
+  render =
+    checkedShellScript
+      {
+        name = "postgrest-docs-render";
+        docs = "Render the diagrams.";
+        workingDir = "/docs/_diagrams";
+        withTmpDir = true;
+      }
+      ''
+        ${texlive.combined.scheme-full}/bin/pdflatex -halt-on-error -output-directory="$tmpdir" db.tex
+        ${imagemagick}/bin/convert -density 300 "$tmpdir/db.pdf" ../_static/db.png
+      '';
+
   server =
     writers.writePython3
       "postgrest-docs-server"
@@ -165,6 +180,7 @@ buildToolbox
       check
       dictcheck
       linkcheck
+      render
       serve
       spellcheck
     ];