Need more standard SIP requests types in the esp_rtc lib

[tdVincentB]

SIP for VoIP calls using the esp_rtc library works but is extremely limited right now, lacking much of the standard features.
The "MESSAGE" type for instance is crucial for certain widely used alarm protocols like SCAIP.
Right now it is impossible to use your library just because of this one missing type...and one must rewrite a whole SIP stack just for this.

Please consider open sourcing your SIP stack because of these very real limitations, or at the bare minimum at least please provide a way for users to expand your library by sending their own standard SIP requests and handling the corresponding responses.

Please consider this request, this is not a gimmick, it can and will impact most users that simply cannot use SIP for commercial products right now with ESP-ADF.

[matz-9]

+1