Recommending a secure source of time

[jhdalek55]

This new issue is actually a re-stating of a long running question, most recently mentioned in the closed Deployment issue #137. That is, pointing towards the best choice for a reliable source of time to be used with Uptane. The Uptane community plans to point toward Network Time Protocol V. 5, an international standard from the Internet Engineering Task Force (IETF), but as of 4-6-23, it was still in draft. Once this standard has been approved, we plan to include it within the Uptane Standard and Deployment Best Practicesas the recommended source of time for Uptane. Until then, this issue serves as a placeholder for resolving this issue, and can host related questions about the use if secure time in Uptane.