Review and fix some incorrect expectations in responses

Following points discussed this morning in NGSI-LD API call (https://docbox.etsi.org/ISG/CIM/05-CONTRIBUTIONS/2023//CIM(23)000143_TTFv2_-_Clarifications_and_final_improvements.pptx):

• slide 4: 207
• slide 5: 204 (silently ignore)
• slide 6: compacted (reason can convey more info, for instance the expanded form, to help users in understanding the problem)