Provide better error description for the "unknown ca" error

... when adding nodes to cluster

Change-Id: I8301c962b94133d972b0e8c7c70dbdc6ffc11e9e
Reviewed-on: https://review.couchbase.org/c/ns_server/+/172012
Well-Formed: Build Bot <[email protected]>
Tested-by: Timofey Barmin <[email protected]>
Reviewed-by: Steve Watanabe <[email protected]>

Author: timofey-barmin

src/ns_error_messages.erl

@@ -40,6 +40,12 @@ connection_error_message({tls_alert, {handshake_failure, Str}}, Host, Port)
     list_to_binary(io_lib:format("Failed to establish TLS connection to ~s:~w. "
                                  "TLS handshake failure (~s)",
                                  [Host, Port, Str]));
+connection_error_message({tls_alert, {unknown_ca, Str}}, Host, Port)
+                                                            when is_list(Str) ->
+    list_to_binary(io_lib:format("Failed to establish TLS connection to ~s:~w. "
+                                 "The certificate is issued by unknown CA or "
+                                 "some of the intermediate certificates are "
+                                 "missing (~s)", [Host, Port, Str]));
 connection_error_message({tls_alert, M}, Host, Port) ->
     list_to_binary(io_lib:format("Failed to establish TLS connection to ~s:~w: ~p", [Host, Port, M]));
 connection_error_message({AFamily, nxdomain}, Host, _Port) ->