fix: do not download more files at runtime

Due to a design choice in Transformers, remote-code embedded in a model on HF is
downloaded at runtime and this cannot be disabled, despite our attempts to
download it at build time. A practical result of this is that the built Docker
container image needs networking access to download the remote code, which is
not ideal.

This fix is a workaround to download the remote code at build time, and embed it
into the model by updating the `config.json` file appropriately. This should
only be needed for Nomic-style models, apparently, since they are some of the
only embedding models that use remote code.

Many thanks to Tom Aarsen for providing me with the steps to fix this.

Relevant issue: UKPLab/sentence-transformers#2613 (comment)

flake.nix

@@ -82,6 +82,7 @@
             buildInputs = [
               python
               embedding-server-py
+              pkgs.gron
             ] ++ pythonLibs;
           } ''
             mkdir -p $out tmp
@@ -92,19 +93,25 @@
             ${python}/bin/python \
               ${embedding-server-py}/libexec/embedding-server.py \
               --save-models-to $out
-            
-            # FIXME: why doesn't the nomic model include this file?
+
+            # https://github.com/UKPLab/sentence-transformers/issues/2613
             cp -v \
               $HF_HOME/hub/models--nomic-ai--nomic-embed-text-v1/snapshots/02d96723811f4bb77a80857da07eda78c1549a4d/configuration_hf_nomic_bert.py \
               $HF_HOME/hub/models--nomic-ai--nomic-embed-text-v1/snapshots/02d96723811f4bb77a80857da07eda78c1549a4d/modeling_hf_nomic_bert.py \
               $out/nomic-embed-text-v1
+
+            gron $out/nomic-embed-text-v1/config.json \
+              | sed -E 's/json\.auto_map\.(.*?)\s=\s".*?\-\-/json\.auto_map\.\1 = "/' \
+              | gron --ungron \
+            > $out/nomic-embed-text-v1/config.json.tmp
+            mv $out/nomic-embed-text-v1/config.json.tmp $out/nomic-embed-text-v1/config.json
           '';
 
         /* finally, just re-package the data with a fixed-output sha256 hash */
         in pkgs.runCommand "model-data" {
           outputHashMode = "recursive";
           outputHashAlgo = "sha256";
-          outputHash = "sha256-nMRQtxrJdLxAnNLGHP61nAePGWJ/ZVG6ad0v9wUBTeY=";
+          outputHash = "sha256-QpmYSk396ShTFyXA9+DWjiGfEuZMSAul9EnOfG6SeRU=";
           passthru = { inherit real-data; };
         } "mkdir -p $out && cp -r ${real-data}/* $out";
       };