urlapi: add curl_url_strerror()

Add curl_url_strerror() to convert CURLUcode into readable string and
facilitate easier troubleshooting in programs using URL API.
Extend CURLUcode with CURLU_LAST for iteration in unit tests.
Update man pages with a mention of new function.
Update example code and tests with new functionality where it fits.

Closes #7605

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/url.c b/lib/url.c
index 37b6c0e84..5c31cadd6 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1954,7 +1954,8 @@ static CURLcode parseurlandfillconn(struct Curl_easy *data,
                      CURLU_DISALLOW_USER : 0) |
                     (data->set.path_as_is ? CURLU_PATH_AS_IS : 0));
     if(uc) {
-      DEBUGF(infof(data, "curl_url_set rejected %s", data->state.url));
+      DEBUGF(infof(data, "curl_url_set rejected %s: %s", data->state.url,
+                   curl_url_strerror(uc)));
       return Curl_uc_to_curlcode(uc);
     }