feat(pre-handlers): Add getAuthBearer function

This commit adds the getAuthBearer function to the pre-handlers package. The function extracts the Bearer token from the authorization header and returns it. If the header is invalid or the token is missing, it returns null.

Example usage:
console.log(this.headers.authorization); // 'Bearer myToken123'
const token = getAuthBearer(this.headers.authorization);
console.log(token); // 'myToken123'

const invalidToken = getAuthBearer('Basic myToken123');
console.log(invalidToken); // null

packages/pre-handlers/src/lib/get-auth-bearer.ts

@@ -0,0 +1,26 @@
+/**
+ * Extracts the Bearer token from the authorization header.
+ *
+ * This function takes an optional authorization header string, extracts the Bearer token, and returns it.
+ * If the header is invalid or the token is missing, it returns null.
+ *
+ * @param {string} [authorizationHeader] - The authorization header string.
+ * @returns {string | null} The extracted Bearer token or null if the header is invalid.
+ *
+ * @example
+ * ```ts
+ * console.log(this.headers.authorization); // 'Bearer myToken123'
+ * const token = getAuthBearer(this.headers.authorization);
+ * console.log(token); // 'myToken123'
+ *
+ * const invalidToken = getAuthBearer('Basic myToken123');
+ * console.log(invalidToken); // null
+ * ```
+ */
+export function getAuthBearer(authorizationHeader?: string): string | null {
+  const auth = authorizationHeader?.split(' ');
+  if (!auth || auth[0].toLowerCase() !== 'bearer' || !auth[1]) {
+    return null;
+  }
+  return auth[1];
+}