`null` gets stripped from user-defined language server configurations

I'm setting configurations through the user-defined language server UI, and find that properties with values explicitly set as null are being stripped before the server receives them:

[Trace - 15:45:59] Sending request 'initialize - (1)'.
Params: {
  <...>,
  "initializationOptions": {
    "field2": "name",
    "field3": "nullaaaa"
  },

[Trace - 15:50:03] Sending notification 'workspace/didChangeConfiguration'
Params: {
  "settings": {
    "fieldB": "name"
  }
}

When I use the server to request the options/settings from the client, the fields which were set to null are now simply missing.

I expect preservation of fields set to null when sent from the client to the server¹. The configuration object that's being retrieved from the UI² shows that null is actually present in the client configuration object before being sent to the server, so something must be happening after reading the configuration.

1. According to the language server specification, the types of initializationOptions and return value of configuration requests are both LSPAny, which is a type union including LSPObject and null. LSPObject is defined as:

   type LSPObject = { [key: string]: LSPAny };

   So, LSPObjects are allowed to have string keys and null values.

2. Using the following modification of com.redhat.devtools.lsp4ij.server.definition.launching.UserDefinedLanguageServerDefinition:

   ...
   + import com.google.gson.JsonElement;
     import com.google.gson.JsonParser;
   ...
     public Object getLanguageServerConfiguration() {
             if (configuration == null && configurationContent != null && !configurationContent.isBlank()) {
                 try {
                     configuration = JsonParser.parseReader(new StringReader(configurationContent));
                 } catch (Exception e) {
                     LOGGER.error("Error while parsing JSON configuration for the language server '" + getId() + "'", e);
                 }
             }
   +         LOGGER.error("CONFIGURATION IS: " + ((JsonElement)configuration).toString());
             return configuration;
     }
   

   IDE Logs:

   SEVERE - com.redhat.devtools.lsp4ij.server.definition.launching.UserDefinedLanguageServerDefinition - CONFIGURATION IS: {"fieldA":null,"fieldB":"name"}
   

Start with UserDefinedLanguageServerDefinition.java and trace how its parsed configuration is passed into initializationOptions and workspace configuration responses. Reproduce the case using a configuration containing a null value, then verify that the value remains present in both messages sent to the language server.