Merge pull request #60 from SOURAV-ROY/ROY

feat: Add project flow documentation

Author: SOURAV-ROY

docs/PROJECT_FLOW.md

@@ -0,0 +1,120 @@
+# Project Flow & Architecture
+
+## Request Lifecycle
+This diagram illustrates how a request travels through the application.
+
+```mermaid
+---
+config:
+  theme: mc
+---
+graph TD
+    Client[Client] -->|HTTP Request| Server[Server index.js]
+    
+    subgraph Middleware_Layer
+        Server --> Security[Security Middleware]
+        Security -->|Helmet, CORS, RateLimit, HPP, XSS| Parser[Body Parsers]
+        Parser -->|JSON, Cookie| Logger[Logger]
+        Logger --> Auth[Auth Middleware]
+    end
+    
+    subgraph Routing_Layer
+        Auth -->|Valid Request| Router{Router}
+        Router -->|/api/v1/bootcamps| BCR[Bootcamps Route]
+        Router -->|/api/v1/courses| CR[Courses Route]
+        Router -->|/api/v1/auth| AR[Auth Route]
+        Router -->|/api/v1/users| UR[Users Route]
+        Router -->|/api/v1/reviews| RR[Reviews Route]
+    end
+    
+    subgraph Controller_Layer
+        BCR --> BCC[Bootcamps Controller]
+        CR --> CC[Courses Controller]
+        AR --> AC[Auth Controller]
+        UR --> UC[Users Controller]
+        RR --> RC[Reviews Controller]
+    end
+    
+    subgraph Data_Layer
+        BCC --> BCM[(Bootcamp Model)]
+        CC --> CM[(Course Model)]
+        AC --> UM[(User Model)]
+        UC --> UM
+        RC --> RM[(Review Model)]
+    end
+    
+    Controller_Layer -->|JSON Response| Client
+    Data_Layer -->|Data| Controller_Layer
+    
+    Server -->|Error| ErrorHandler[Error Handler Middleware]
+    ErrorHandler -->|Error Response| Client
+```
+
+## Data Models (ERD)
+Relationships between the main data entities.
+
+```mermaid
+erDiagram
+    User ||--o{ Bootcamp : "publishes"
+    User ||--o{ Review : "writes"
+    Bootcamp ||--o{ Course : "offers"
+    Bootcamp ||--o{ Review : "receives"
+    
+    User {
+        string name
+        string email
+        string role "user|publisher"
+        string password
+    }
+    
+    Bootcamp {
+        string name
+        string description
+        string website
+        string phone
+        string email
+        string address
+        string[] careers
+        boolean housing
+        boolean jobAssistance
+        boolean jobGuarantee
+        boolean acceptGi
+    }
+    
+    Course {
+        string title
+        string description
+        string weeks
+        string tuition
+        string minimumSkill
+        boolean scholarshipAvailable
+    }
+    
+    Review {
+        string title
+        string text
+        number rating
+    }
+```
+
+## Key Components
+
+### Middleware
+- **Security**: `helmet`, `cors`, `express-rate-limit`, `hpp`, `xss-clean` protect the app.
+- **Auth**: `protect` verifies JWT tokens, `authorize` checks user roles.
+- **Advanced Results**: Handles pagination, filtering, and sorting for list endpoints.
+- **Error Handler**: Centralized error handling for consistent responses.
+
+### Controllers
+- **Auth**: Registration, login, logout, password management.
+- **Bootcamps**: CRUD operations for bootcamps, photo upload, geospatial search.
+- **Courses**: CRUD operations for courses, associated with bootcamps.
+- **Users**: Admin management of users.
+- **Reviews**: User reviews for bootcamps.
+
+### Models
+- **User**: Stores user information, authentication, and roles.
+- **Bootcamp**: Stores bootcamp details, location, and associated courses.
+- **Course**: Stores course details, associated with bootcamps.
+- **Review**: Stores user reviews for bootcamps.
+