URL refactor part 1.

This eliminates most (but not all) of the dynamic allocations
associated with URL objects.  A number of convenience fields
on the URL are removed, but we are able to use common buffer
for most of the details.

docs/ref/api/url.md

@@ -14,13 +14,11 @@ that are not part of the IETF standards.
 typedef struct nng_url {
     const char *u_scheme;
     char       *u_userinfo;
-    char       *u_host;
     char       *u_hostname;
     uint16_t   u_port;
     char       *u_path;
     char       *u_query;
     char       *u_fragment;
-    char       *u_requri;
 } nng_url;
 ```
 
@@ -29,17 +27,18 @@ typedef struct nng_url {
 Applications may access individual fields, but must not free or
 alter them, as the underlying memory is managed by the library.
 
+Additionally applications must not depend on the size of this structure.
+Obtain one using `nng_parse_url`.
+
 The fields of an `nng_url` object are as follows:
 
 - `u_scheme`: The URL scheme, such as "http" or "inproc". Always lower case. This will never be `NULL`.
 - `u_userinfo`: This username and password if supplied in the URL string. Will be `NULL` when not present.
-- `u_host`: The full host part of the URL, including the port if present (separated by a colon.)
 - `u_hostname`: The name of the host, and may be the empty string in some cases.
 - `u_port`: The port. May be zero if irrelevant or not specified.
 - `u_path`: The path, typically used with HTTP or WebSockets. Will be empty string if not specified.
 - `u_query`: The query info (typically following `?` in the URL.) Will be `NULL` if not present.
 - `u_fragment`: This is used for specifying an anchor, the part after `#` in a URL. Will be `NULL` if not present.
-- `u_requri`: The full Request-URI. Will be the empty string if not specified.
 
 > [!NOTE]
 > Other fields may also be present, but only those documented here are safe for application use.

docs/ref/migrate/nng1.md

@@ -160,11 +160,20 @@ A number of the [statistics][statistic] functions take, or return, `const nng_st
 of plain `nng_stat *`. The ABI has not changed, but it may be necessary to declare
 certain methods variables `const` to avoid warnings about misuse of `const`.
 
-## Url Structure Members
+## Wildcards Not Valid in URLs
+
+The use of `*` to act as a wild card meaning all local interface addresses
+is removed. The empty string already performs this function, and unlike
+`*` is RFC compliant.
+
+## URL Structure Members
 
 The details of [`nng_url`] have changed as follows:
 
 - `u_port` is no longer a string, but a `uint16_t`
-- `u_scheme` is a const char \*
+- `u_scheme` is a `const char *`
+- `u_requri` is removed - it can be easily formulated from the other fields.
+- `u_host` is removed - use `u_hostname` and `u_port` to construct if needed
+- `u_rawurl` is removed - a "cooked" URL can be obtained from the new [`nng_url_sprintf`] function.
 
 {{#include ../xref.md}}

include/nng/nng.h

@@ -1085,14 +1085,16 @@ enum nng_errno_enum {
 typedef struct nng_url {
 	char       *u_rawurl;   // never NULL
 	const char *u_scheme;   // never NULL
-	char       *u_userinfo; // will be NULL if not specified
-	char       *u_host;     // including colon and port
+	const char *u_userinfo; // will be NULL if not specified
 	char       *u_hostname; // name only, will be "" if not specified
 	uint16_t    u_port;  // port, may be zero for schemes that do not use
 	char       *u_path;  // path, will be "" if not specified
 	char       *u_query; // without '?', will be NULL if not specified
 	char       *u_fragment; // without '#', will be NULL if not specified
-	char *u_requri; // includes query and fragment, "" if not specified
+	// these members are private
+	char  *u_buffer;
+	size_t u_bufsz;
+	char   u_static[NNG_MAXADDRLEN]; // Most URLs fit within this
 } nng_url;
 
 // nng_url_parse parses a URL string into a structured form.