feat: add config for embedding model (#12120)

This PR adds the ability to modify the embedding model used by Captain
AI.Previously, the embedding model was hardcoded which led to errors when
you used a different API provider which did not support that specific
embedding model.

Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

enterprise/app/services/captain/llm/embedding_service.rb

@@ -3,9 +3,11 @@ require 'openai'
 class Captain::Llm::EmbeddingService < Llm::BaseOpenAiService
   class EmbeddingsError < StandardError; end
 
-  DEFAULT_MODEL = 'text-embedding-3-small'.freeze
+  def self.embedding_model
+    @embedding_model = InstallationConfig.find_by(name: 'CAPTAIN_EMBEDDING_MODEL')&.value.presence || OpenAiConstants::DEFAULT_EMBEDDING_MODEL
+  end
 
-  def get_embedding(content, model: DEFAULT_MODEL)
+  def get_embedding(content, model: self.class.embedding_model)
     response = @client.embeddings(
       parameters: {
         model: model,