Refactor the consultations

[khavinshankar]

Context:
Currently, in Care, consultations take care of an entire visit and there is no separation between multiple doctor appointments.

Idea:
Have an encounter that encompasses the entire visit of a patient (something similar to existing consultations) and within them a way to group one or more doctor consultations.

Checkout encounters and appointments in FHIR for initial reference:

• https://build.fhir.org/encounter.html
• https://build.fhir.org/appointment.html

TODO:

• Rename existing consultation to encounter
• Design actual consultation

Needs further discussions before getting started