Implement a better API

[ignacio-chiazzo]

Solves #155

This PR introduces a new API to interact with the different API concerns. Instead of creating a new object per each area (media, messages, business_profiles etc) we can just call client. with the api name.

Before:

  messages_api = WhatsappSdk::Api::Messages.new
  phone_numbers_api = WhatsappSdk::Api::PhoneNumbers.new
  business_profile_api = WhatsappSdk::Api::BusinessProfile.new
  templates_api = WhatsappSdk::Api::Templates.new

  messages_api.get 
  #...
  phone_numbers_api.registered_number ...

After:

client.messages.send_text(....)

client.media.upload(....)

client.business_profiles.details

This PR also deprecates some methods:

Concern	Before	After
Business Profile	client.business_profiles.details	client.business_profiles.get
Phone Numbers	client.phone_numbers.registered_numbers	client.phone_numbers.list
Phone Numbers	client.phone_numbers.registered_number	client.phone_numbers.get
Templates	client.templates.templates	client.templates.list
Media	client.medias.media	client.medias.get

Note: I still maintain the old methods but raised a deprecated warning. I plan to remove them as part of 1.0.0.

To see the final API, see the README file.