Add phone voicemail webhook events

[ivan-pavlik]

This PR adds the following webhook events:

• phone.voicemail_deleted
• phone.voicemail_permanently_deleted
• phone.voicemail_received
• phone.voicemail_received_for_access_member
• phone.voicemail_transcript_completed

Models:

• PhoneVoicemailEvent: base model with callee's AccountId property.
• PhoneVoicemailReceivedForAccessMemberEvent is not inherited from PhoneVoicemailEvent as here AccountId represents access member's account id.
• merged PhoneCallRecordingCalleeNumberType and PhoneCallRecordingCallerNumberType into PhoneCallNumberType enum: values are the same (though 'callee' case has one more possible number type), and it is not related to recordings only. Note that this is a breaking change (if library client explicitly used one of the old enums they should change it to the new enum).
• new models for the voicemail and transcript. I see some differences in the voicemail properties returned by webhook events and API endpoints, so to simplify adding these endpoints (at some point later on) I've added VoicemailBase with the properties common for voicemail webhooks and endpoints, and child WebhookVoicemail with webhook specific properties.

Unit tests:

• added unit tests for the new webhook events
• adjusted and aligned property values in phone voicemail webhook events json data to simplify checks

[Jericho]

Looks good to me!
Thank you for your contribution.

[Jericho]

Another excellent PR!

[Jericho]

🎉 This issue has been resolved in version 0.102.0 🎉

The release is available on:

• GitHub Release
• NuGet Package

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