Add Cookbook C01-C19 (draft)

docs-src/pages/en/cookbook/c06-bearer-token.md

@@ -0,0 +1,50 @@
+---
+title: "C06. Call an API with a Bearer Token"
+order: 6
+status: "draft"
+---
+
+For Bearer token authentication — common in OAuth 2.0 and modern Web APIs — use `set_bearer_token_auth()`. Pass the token and cpp-httplib builds the `Authorization: Bearer <token>` header for you.
+
+## Basic usage
+
+```cpp
+httplib::Client cli("https://api.example.com");
+cli.set_bearer_token_auth("eyJhbGciOiJIUzI1NiIs...");
+
+auto res = cli.Get("/me");
+if (res && res->status == 200) {
+  std::cout << res->body << std::endl;
+}
+```
+
+Set it once and every subsequent request carries the token. This is the go-to pattern for token-based APIs like GitHub, Slack, or your own OAuth service.
+
+## Per-request usage
+
+When you want the token on only one request — or need a different token per request — pass it via headers.
+
+```cpp
+httplib::Headers headers = {
+  httplib::make_bearer_token_authentication_header(token),
+};
+auto res = cli.Get("/me", headers);
+```
+
+`make_bearer_token_authentication_header()` builds the `Authorization` header for you.
+
+## Refresh the token
+
+When a token expires, just call `set_bearer_token_auth()` again with the new one.
+
+```cpp
+if (res && res->status == 401) {
+  auto new_token = refresh_token();
+  cli.set_bearer_token_auth(new_token);
+  res = cli.Get("/me");
+}
+```
+
+> **Warning:** A Bearer token is itself a credential. Always send it over HTTPS, and never hard-code it into source or config files.
+
+> To set multiple headers at once, see C03. Set Default Headers.