Merge branch 'mc/credential-helper-www-authenticate'

Allow information carried on the WWW-AUthenticate header to be
passed to the credential helpers.

* mc/credential-helper-www-authenticate:
  credential: add WWW-Authenticate header to cred requests
  http: read HTTP WWW-Authenticate response headers
  t5563: add tests for basic and anoymous HTTP access

credential.h

@@ -2,6 +2,7 @@
 #define CREDENTIAL_H
 
 #include "string-list.h"
+#include "strvec.h"
 
 /**
  * The credentials API provides an abstracted way of gathering username and
@@ -115,6 +116,20 @@ struct credential {
 	 */
 	struct string_list helpers;
 
+	/**
+	 * A `strvec` of WWW-Authenticate header values. Each string
+	 * is the value of a WWW-Authenticate header in an HTTP response,
+	 * in the order they were received in the response.
+	 */
+	struct strvec wwwauth_headers;
+
+	/**
+	 * Internal use only. Keeps track of if we previously matched against a
+	 * WWW-Authenticate header line in order to re-fold future continuation
+	 * lines into one value.
+	 */
+	unsigned header_is_last_match:1;
+
 	unsigned approved:1,
 		 configured:1,
 		 quit:1,
@@ -132,6 +147,7 @@ struct credential {
 #define CREDENTIAL_INIT { \
 	.helpers = STRING_LIST_INIT_DUP, \
 	.password_expiry_utc = TIME_MAX, \
+	.wwwauth_headers = STRVEC_INIT, \
 }
 
 /* Initialize a credential structure, setting all fields to empty. */