res_pjsip: Add handling for incoming unsolicited MWI NOTIFY

A new endpoint parameter "incoming_mwi_mailbox" allows Asterisk to
receive unsolicited MWI NOTIFY requests and make them available to
other modules via the stasis message bus.

res_pjsip_pubsub has a new handler "pubsub_on_rx_mwi_notify_request"
that parses a simple-message-summary body and, if
endpoint->incoming_mwi_account is set, calls ast_publish_mwi_state
with the voice-message counts from the message.

Change-Id: I08bae3d16e77af48fcccc2c936acce8fc0ef0f3c

include/asterisk/res_pjsip.h

@@ -804,6 +804,8 @@ struct ast_sip_endpoint {
 	unsigned int refer_blind_progress;
 	/*! Whether to notifies dialog-info 'early' on INUSE && RINGING state */
 	unsigned int notify_early_inuse_ringing;
+	/*! If set, we'll push incoming MWI NOTIFYs to stasis using this mailbox */
+	AST_STRING_FIELD_EXTENDED(incoming_mwi_mailbox);
 };
 
 /*! URI parameter for symmetric transport */

include/asterisk/strings.h

@@ -1383,4 +1383,24 @@ char *ast_generate_random_string(char *buf, size_t size);
  */
 int ast_strings_match(const char *left, const char *op, const char *right);
 
+/*!
+ * \brief Read lines from a string buffer
+ * \since 13.18.0
+ *
+ * \param buffer [IN/OUT] A pointer to a char * string with either Unix or Windows line endings
+ *
+ * \return The "next" line
+ *
+ * \warning The original string and *buffer will be modified.
+ *
+ * \details
+ * Both '\n' and '\r\n' are treated as single delimiters but consecutive occurrances of
+ * the delimiters are NOT considered to be a single delimiter.  This preserves blank
+ * lines in the input.
+ *
+ * MacOS line endings ('\r') are not supported at this time.
+ *
+ */
+char *ast_read_line_from_buffer(char **buffer);
+
 #endif /* _ASTERISK_STRINGS_H */