Checklist before requesting a review

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.
• I have added tests that prove my fix is effective or that my feature works.

Description

• New links for Certificates, Appliances, KB Articles, Domains, Lines, Contracts, and Projects
• New for ApplianceEnvironment, Network, DomainRelation, LineOperator, DomainRecord, ExternalLink, ManualLink
• Added previously missing endpoints for SLA, OLA, SlaLevel and OlaLevel
• Minor changes to better support mapped array values.
• Allow optionally accepting RFC 3339 datetime values as inputs to match the values coming out from the API