docs: add architecture diagram document

apps/api/docs/block-diagram.md

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+# **Block Diagram**
+
+## **Introduction**
+
+This document provides a concise block diagram illustrating the architecture of our software application, Transcript Summarization. The diagram outlines the key components and their interactions to help you better understand how the application functions.
+
+**Block Diagram Overview:**
+
+The block diagram represents the software application's architecture in a visual format, making it easier to grasp its structure and functionality.
+
+## Block Diagram
+
+![Block Diagram](./assets/transcript-summarization-block-diagram.jpg)
+
+## Components and Functionalities
+
+1. **User/PWA**
+    - This component is responsible for making the request to the transcript summarization API with a VTT file uploaded by the user.
+
+### **2\. GraphQL API**
+
+    - The core component, created with NestJS, is responsible for accepting the incoming requests made by the user/application for creating a transcript summary.
+    - A status response is sent back to the user/PWA to signify if the file has been successfully summarized or if any errors were encountered.
+    - Upon receiving the request, the API stores the received job ID and other necessary details in the database.
+
+### **3\. Database TypeORM**
+
+- The MariaDB database is responsible for holding the records of uploaded transcripts along with all other required details about them such as the jobId, CreatedAt time, CreatedBy username etc.
+The records in the database are updated with the summarized file download link received from the server upon conversion success.
+
+### **4\. Cron Job Scheduler**
+
+A scheduled cron fetches all the uploaded transcripts in the pending status from the database and adds their Job IDs to the queue for processing.
+
+### **5\. Queue**
+
+- A queue is maintained to allow processing of transcript records one by one.
+- These queues are implemented using Bull Queue.
+- The queue receives the Job ID of the transcript to be summarized and fetches its File data from the database using this Job ID to pass it onto the service.
+
+### **6\. OpenAI Python Script**
+
+- The script holds the business logic for generating the summary of the uploaded transcript.
+- Upon success/failure, the response is sent back to update the status of the job ID
+
+## Data Flow
+
+- User interacts with the progressive web App to upload transcript files.
+- NestJS backend receives the file upload request and enqueues a job in the Bull queue for transcript summarization.
+- Cron job scheduler triggers a job every second
+- The queue processor picks up jobs from the Bull queue and executes transcript summarization of the uploaded file using the OpenAI Python script.
+- On success, summarized files are stored on a server, and a download link is generated using a REST API Endpoint which is stored in MariaDB database
+- A download link through a REST API endpoint is made available for users to download the summarized file.
+
+## **Conclusion**
+
+This block diagram serves as a valuable resource for understanding the architecture of our software application. It highlights the core components, their interactions, and the flow of data within the application.