Function extractTokenFromHeader

extractTokenFromHeader(authHeader?: string): null | string
Extract Bearer token from Authorization header

Parses the Authorization header to extract JWT tokens following the Bearer token authentication scheme. Validates the header format and returns the token portion, or null if the header is missing or malformed.

This utility function is used by authentication middleware to extract tokens from HTTP requests for verification. It handles the standard "Bearer " format and provides safe parsing with null returns for invalid formats.
Parameters
- OptionalauthHeader: string
  Authorization header value (optional)
Returns null | string
Extracted token string or null if header is invalid/missing
Example
```
// Extract token from request header
const authHeader = req.headers.authorization; // 'Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...'
const token = extractTokenFromHeader(authHeader);
console.log(token); // 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...'
```
Example
```
// Handle missing or invalid headers
extractTokenFromHeader(undefined);           // returns null
extractTokenFromHeader('Invalid header');    // returns null
extractTokenFromHeader('Bearer');            // returns null
extractTokenFromHeader('Basic dXNlcjpwYXNz'); // returns null (wrong scheme)
```
- Defined in src/shared/utils/auth.ts:435