Add push contacts for rapidpro

[megh-k]

The push_contact functionality was necessary for the Open Case button functionality. For this to work a few things are necessary, as summarised below:

• URNs need to be synced to CasePro to check if the URN already exists in both CasePro and RapidPro.
• URNs also needed to be hidden from the UI for privacy. I removed the urn.path from the frontend but left the placeholder.
• push_contact checks for the contact in RapidPro by the URN, if it doesn't exist, the contact is created in RapidPro and the RapidPro uuid is returned.
• get_or_create_from_urn looks for the contact in CasePro by the URN, if it does not exist, it gets the contact from RapidPro and its uuid, it then looks for the CasePro contact by the uuid to avoid duplicated, if it still doesn't exist, a new CasePro contact is made and the uuid is set to match the RapidPro uuid.
• As we make use of WhatsApp, the WhatsApp scheme is also added as a valid scheme.
• The test were also updated to accommodate the new functionality.

[codecov[bot]]

Codecov Report

Merging #371 (c7a4f04) into main (f439f68) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #371   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           72        72           
  Lines         4670      4680   +10     
=========================================
+ Hits          4670      4680   +10     

Impacted Files	Coverage Δ
casepro/backend/__init__.py	100.00% <100.00%> (ø)
casepro/backend/rapidpro.py	100.00% <100.00%> (ø)
casepro/cases/views.py	100.00% <100.00%> (ø)
casepro/contacts/models.py	100.00% <100.00%> (ø)
casepro/contacts/views.py	100.00% <100.00%> (ø)

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