fix(review): drop <stanza-id by> checks overlapping with PR #105

After review of PR #105 (upstream-full merge) it became clear the
<stanza-id by> validation for MUC and 1:1 chat is already added there
via upstream profanity. Keeping both versions would conflict on merge.

Removed from this PR:
  - _handle_groupchat <stanza-id by == room JID> check
    (identical to PR #105)
  - _handle_chat <stanza-id by == my_domain> check
    (PR #105 uses equals_our_barejid(by) instead — defer to upstream)
  - STANZA_ATTR_BY define (no longer referenced)

Kept (PR #105 does NOT touch these):
  - XEP-0203 §4 <delay from=?> validation in _handle_groupchat,
    _handle_chat, _handle_muc_private_message
  - stanza_get_oldest_delay_from() helper + NULL-tmp guard bug fix
    in stanza_get_oldest_delay()

Also applied review fixes:
  - Add g_date_time_new_now_local() fallback in
    _handle_muc_private_message so timestamp is never NULL
  - Change stanza_get_delay_from signature to const char* const from,
    eliminating (gchar*) casts at call sites

src/xmpp/message.c

@@ -1090,16 +1090,12 @@ _handle_groupchat(xmpp_stanza_t* const stanza)
         message->id = strdup(id);
     }
 
-    // XEP-0359 §5: only accept <stanza-id> whose 'by' matches the MUC room
     char* stanzaid = NULL;
     xmpp_stanza_t* stanzaidst = xmpp_stanza_get_child_by_name_and_ns(stanza, STANZA_NAME_STANZA_ID, STANZA_NS_STABLE_ID);
     if (stanzaidst) {
-        const char* by = xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_BY);
-        if (by && g_strcmp0(by, from_jid->barejid) == 0) {
-            stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
-            if (stanzaid) {
-                message->stanzaid = strdup(stanzaid);
-            }
+        stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
+        if (stanzaid) {
+            message->stanzaid = strdup(stanzaid);
         }
     }
 
@@ -1288,12 +1284,13 @@ _handle_muc_private_message(xmpp_stanza_t* const stanza)
 #endif
 
     // XEP-0203 §4: only trust <delay> from a server domain.
-    {
-        const char* my_domain = connection_get_domain();
-        message->timestamp = stanza_get_delay_from(stanza, (gchar*)my_domain);
-        if (!message->timestamp && message->from_jid->domainpart) {
-            message->timestamp = stanza_get_delay_from(stanza, message->from_jid->domainpart);
-        }
+    const char* my_domain = connection_get_domain();
+    message->timestamp = stanza_get_delay_from(stanza, my_domain);
+    if (!message->timestamp && message->from_jid->domainpart) {
+        message->timestamp = stanza_get_delay_from(stanza, message->from_jid->domainpart);
+    }
+    if (!message->timestamp) {
+        message->timestamp = g_date_time_new_now_local();
     }
     message->body = xmpp_message_get_body(stanza);
 
@@ -1418,17 +1415,13 @@ _handle_chat(xmpp_stanza_t* const stanza, gboolean is_mam, gboolean is_carbon, c
             log_warning("MAM received with no result id");
         }
     } else {
-        // XEP-0359 §5: only accept <stanza-id> whose 'by' matches our server
+        // live messages use XEP-0359 <stanza-id>
         char* stanzaid = NULL;
         xmpp_stanza_t* stanzaidst = xmpp_stanza_get_child_by_name_and_ns(stanza, STANZA_NAME_STANZA_ID, STANZA_NS_STABLE_ID);
         if (stanzaidst) {
-            const char* by = xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_BY);
-            const char* my_domain = connection_get_domain();
-            if (by && my_domain && g_strcmp0(by, my_domain) == 0) {
-                stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
-                if (stanzaid) {
-                    message->stanzaid = strdup(stanzaid);
-                }
+            stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
+            if (stanzaid) {
+                message->stanzaid = strdup(stanzaid);
             }
         }
     }
@@ -1449,7 +1442,7 @@ _handle_chat(xmpp_stanza_t* const stanza, gboolean is_mam, gboolean is_carbon, c
         // XEP-0203 §4: only trust <delay> from a server domain, not from
         // the remote client which could forge an arbitrary timestamp.
         const char* my_domain = connection_get_domain();
-        message->timestamp = stanza_get_delay_from(stanza, (gchar*)my_domain);
+        message->timestamp = stanza_get_delay_from(stanza, my_domain);
         if (!message->timestamp && jid->domainpart) {
             message->timestamp = stanza_get_delay_from(stanza, jid->domainpart);
         }

src/xmpp/stanza.c

@@ -1183,7 +1183,7 @@ _stanza_get_delay_timestamp_xep0091(xmpp_stanza_t* const x_stanza)
 }
 
 GDateTime*
-stanza_get_delay_from(xmpp_stanza_t* const stanza, gchar* from)
+stanza_get_delay_from(xmpp_stanza_t* const stanza, const char* const from)
 {
     xmpp_stanza_t* delay = NULL;
 

src/xmpp/stanza.h

@@ -196,7 +196,6 @@
 #define STANZA_ATTR_FILENAME       "filename"
 #define STANZA_ATTR_SIZE           "size"
 #define STANZA_ATTR_CONTENTTYPE    "content-type"
-#define STANZA_ATTR_BY             "by"
 #define STANZA_ATTR_LABEL          "label"
 
 #define STANZA_TEXT_AWAY   "away"
@@ -330,7 +329,7 @@ xmpp_stanza_t* stanza_create_mediated_invite(xmpp_ctx_t* ctx, const char* const
 gboolean stanza_contains_chat_state(xmpp_stanza_t* stanza);
 
 GDateTime* stanza_get_delay(xmpp_stanza_t* const stanza);
-GDateTime* stanza_get_delay_from(xmpp_stanza_t* const stanza, gchar* from);
+GDateTime* stanza_get_delay_from(xmpp_stanza_t* const stanza, const char* const from);
 GDateTime* stanza_get_oldest_delay(xmpp_stanza_t* const stanza);
 GDateTime* stanza_get_oldest_delay_from(xmpp_stanza_t* const stanza, const char* const from);