Create comprehensive root-level .env.template file

- Add all required environment variables for Docker Compose setup
- Include clear comments explaining each variable and its purpose
- Organize variables into logical sections (Registry, Auth, Security, Cognito, etc.)
- Provide setup instructions and references to documentation
- Include generation instructions for SECRET_KEY
- Add optional variables like GitHub OAuth and API keys
- Reference docs/cognito.md for detailed Cognito setup
- Compatible with build_and_run.sh script
- Addresses issue #17

Author: aarora79

.env.template

@@ -0,0 +1,85 @@
+# =============================================================================
+# MCP Gateway Registry - Environment Configuration Template
+# =============================================================================
+# Copy this file to .env and fill in your actual values
+# The build_and_run.sh script will automatically generate a SECRET_KEY if not provided
+
+# =============================================================================
+# REGISTRY CONFIGURATION
+# =============================================================================
+# Registry URL - typically http://localhost:7860 for local development
+REGISTRY_URL=http://localhost:7860
+
+# Admin credentials for the web UI and API access
+# Change these to secure values for production
+ADMIN_USER=admin
+ADMIN_PASSWORD=your-secure-password-here
+
+# =============================================================================
+# AUTH SERVER CONFIGURATION
+# =============================================================================
+# Internal auth server URL (used by containers to communicate)
+AUTH_SERVER_URL=http://auth-server:8888
+
+# External auth server URL (used by clients outside the container network)
+# For local development: http://localhost:8888
+# For production: https://your-domain.com or http://your-ec2-instance.amazonaws.com
+AUTH_SERVER_EXTERNAL_URL=http://localhost:8888
+
+# =============================================================================
+# SECURITY CONFIGURATION
+# =============================================================================
+# Secret key for session cookie signing and other cryptographic operations
+# Will be auto-generated by build_and_run.sh if not provided
+# To generate manually: python -c 'import secrets; print(secrets.token_hex(32))'
+SECRET_KEY=
+
+# =============================================================================
+# AWS COGNITO OAUTH2 CONFIGURATION
+# =============================================================================
+# AWS region where your Cognito User Pool is located
+AWS_REGION=us-east-1
+
+# Cognito User Pool ID - found in AWS Console under Cognito User Pools
+# Format: us-east-1_XXXXXXXXX
+COGNITO_USER_POOL_ID=your-cognito-user-pool-id-here
+
+# Cognito App Client ID - found in your User Pool's App Clients section
+COGNITO_CLIENT_ID=your-cognito-client-id-here
+
+# Cognito App Client Secret - found in your User Pool's App Clients section
+# Note: Only required if your app client has a secret configured
+COGNITO_CLIENT_SECRET=your-cognito-client-secret-here
+
+# =============================================================================
+# GITHUB OAUTH CONFIGURATION (Optional)
+# =============================================================================
+# GitHub OAuth App credentials - only needed if using GitHub authentication
+# Leave empty if only using Cognito authentication
+GITHUB_CLIENT_ID=
+GITHUB_CLIENT_SECRET=
+
+# =============================================================================
+# EXTERNAL API KEYS
+# =============================================================================
+# Polygon.io API key for financial data MCP server
+# Get your free API key from: https://polygon.io/dashboard/signup
+# The fininfo MCP server will still start without this but will return 401 errors
+POLYGON_API_KEY=your-polygon-api-key-here
+
+# =============================================================================
+# SETUP INSTRUCTIONS
+# =============================================================================
+# 1. Copy this file: cp .env.template .env
+# 2. Fill in the required values above
+# 3. For Cognito setup, see: docs/cognito.md
+# 4. Run: ./build_and_run.sh
+# 5. Access the registry at: http://localhost:7860 (or your configured URL)
+#
+# Required for basic functionality:
+# - ADMIN_PASSWORD (set to a secure value)
+# - COGNITO_USER_POOL_ID, COGNITO_CLIENT_ID, COGNITO_CLIENT_SECRET
+#
+# Optional but recommended:
+# - POLYGON_API_KEY (for financial data tools)
+# - AUTH_SERVER_EXTERNAL_URL (for external client access)