Make streaming optional for the /chat endpoint (#287)

* Update the /chat endpoint to conditionally support streaming

- If streams are enabled, return the threadgenerator as it does currently
- If stream is disabled, return a JSON response with the response/compiled references separated out
- Correspondingly, update the chat.html UI to use the streamed API, as well as Obsidian
- Rename chat/init/ to chat/history

* Update khoj.el to use the /history endpoint

- Update corresponding unit tests to use stream=true

* Remove & from call to /chat for obsidian

* Abstract functions out into a helpers.py file and clean up some of the error-catching

src/interface/obsidian/src/chat_modal.ts

@@ -140,7 +140,7 @@ export class KhojChatModal extends Modal {
 
     async getChatHistory(): Promise<void> {
         // Get chat history from Khoj backend
-        let chatUrl = `${this.setting.khojUrl}/api/chat/init?client=obsidian`;
+        let chatUrl = `${this.setting.khojUrl}/api/chat/history?client=obsidian`;
         let response = await request(chatUrl);
         let chatLogs = JSON.parse(response).response;
         chatLogs.forEach((chatLog: any) => {
@@ -157,7 +157,7 @@ export class KhojChatModal extends Modal {
 
         // Get chat response from Khoj backend
         let encodedQuery = encodeURIComponent(query);
-        let chatUrl = `${this.setting.khojUrl}/api/chat?q=${encodedQuery}&n=${this.setting.resultsCount}&client=obsidian`;
+        let chatUrl = `${this.setting.khojUrl}/api/chat?q=${encodedQuery}&n=${this.setting.resultsCount}&client=obsidian&stream=true`;
         let responseElement = this.createKhojResponseDiv();
 
         // Temporary status message to indicate that Khoj is thinking