DEVX-7117/DEVX-7205/DEVX-7199/DEVX-7298: Add Verify v2

[superchilled]

What this PR does

Implements the Verify v2 API in the Ruby SDK by doing the following:

• Defines a Verify2 class with the following methods:
  • start_verification: starts a verification request
  • check_code checks a code against a specific verification_id
  • cancel_verification_request cancels an active verification request via a specific verification_id
  • start_verification_options: instantiates a StartVerificationOptions object
  • workflow: instantiates a Workflow object
  • workflow_builder: returns the WorkflowBuilder class
• Defines classes for each workflow channel:
• Defines the following supporting classes for setting options and creating workflows:
  • StartVerificationOptions
  • Workflow
  • WorkflowBuilder
• Updates the Vonage:Client class to add a verify2 method (which instantiates a new Verify2 object, or returns an existing one if already created)
• Updates the conditional logic in the Vonage::Namespace#parse method to account for the fact that the Verify v2 API code check endpoint returns a HTTP response with a 200 status but no body
• Adds unit tests for all the new functionality.
• Updates the README document to outline how to use the added functionality

[codecov-commenter]

Codecov Report

Merging #261 (e03165f) into dev (1e33d4c) will increase coverage by 0.21%. The diff coverage is 99.52%.

:exclamation: Current head e03165f differs from pull request most recent head d989a61. Consider uploading reports for the commit d989a61 to get more accurate results

@@            Coverage Diff             @@
##              dev     #261      +/-   ##
==========================================
+ Coverage   97.73%   97.95%   +0.21%     
==========================================
  Files          71       81      +10     
  Lines        1457     1660     +203     
==========================================
+ Hits         1424     1626     +202     
- Misses         33       34       +1     

Impacted Files	Coverage Δ
lib/vonage/namespace.rb	100.00% <ø> (ø)
lib/vonage/verify2/workflow.rb	93.75% <93.75%> (ø)
lib/vonage/client.rb	100.00% <100.00%> (ø)
lib/vonage/messaging/channels/viber.rb	100.00% <100.00%> (ø)
lib/vonage/messaging/channels/whats_app.rb	100.00% <100.00%> (ø)
lib/vonage/numbers.rb	100.00% <100.00%> (ø)
lib/vonage/verify2.rb	100.00% <100.00%> (ø)
lib/vonage/verify2/channels/email.rb	100.00% <100.00%> (ø)
lib/vonage/verify2/channels/silent_auth.rb	100.00% <100.00%> (ø)
lib/vonage/verify2/channels/sms.rb	100.00% <100.00%> (ø)
... and 5 more

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[superchilled]

Note: waiting to merge this until the product is GA.