Handle multipart messages

[samer-12]

NoRefNo Received message with id=5DA6CE82 from NULLREGISTER sip:cloudpbx-t.ims.mnc002.mcc238.3gppnetwork.org;lr SIP/2.0To: sip:+4577997757@testlab.ims.mnc002.mcc238.3gppnetwork.orgFrom: ;tag=532a84860bf5d862413c35abd116e9b3Call-ID: 2186d2fdd85e8245bf5ef7c0838d55a7CSeq: 1 REGISTERMax-Forwards: 70Via: SIP/2.0/TCP 10.101.135.125:5060;branch=z9hG4bK3a29480ce554bd4fe8cb1eacde948304l555555qaaaaacaaaaaaaaaaaaaabcyof3Zqkv7a0cnblbibaaiagaaaaacqaaaaaaaaaaaaaa;rport=39204Route: <sip:cloudpbx-t.ims.mnc002.mcc238.3gppnetwork.org;lr>Contact: Content-Type: multipart/mixed;boundary=1544012072Expires: 0Content-Length: 1317--1544012072Content-Type:message/sipContent-Length:477REGISTER sip:xcee01scscf01.ims.mnc002.mcc238.3gppnetwork.org SIP/2.0To: sip:+4577997757@testlab.ims.mnc002.mcc238.3gppnetwork.orgFrom: sip:+4577997757@testlab.ims.mnc002.mcc238.3gppnetwork.org;tag=abd1f2a01d65406189bd09a13a2db5f1Call-ID: f4ee8ee59c5fc26a04b70ad38199f54dCSeq: 1 REGISTERMax-Forwards: 70Content-Length: 0Via: SIP/2.0/TCP xcee01scscf01.ims.mnc002.mcc238.3gppnetwork.org;branch=z9hG4bKd388bdcc2813a597bb854bee397638bfgContact: *Expires: 0--1544012072Content-Type:message/sipContent-Length:698SIP/2.0 200 OKTo: sip:+4577997757@testlab.ims.mnc002.mcc238.3gppnetwork.org;tag=f4ee8ee59c5fc26a04b70ad38199f54dFrom: sip:+4577997757@testlab.ims.mnc002.mcc238.3gppnetwork.org;tag=abd1f2a01d65406189bd09a13a2db5f1Call-ID: f4ee8ee59c5fc26a04b70ad38199f54dCSeq: 1 REGISTERContent-Length: 0Via: SIP/2.0/TCP xcee01scscf01.ims.mnc002.mcc238.3gppnetwork.org;branch=z9hG4bKd388bdcc2813a597bb854bee397638bfgContact: sip:238025030001097@10.236.8.6:6100;EriBindingId=31450692410109;eribind-generated-at=10.101.139.20;expires=0;q=1;+sip.instance="";+g.3gpp.accesstype="cellular";+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";+g.3gpp.smsip--1544012072--

[samer-12]

Will require refactor of sip header and body, as body may contain sip header fields

[samer-12]

Should be handeled in issue #111