fix(pedm): ensure get_last_request_time has a value

[Richard Markiewicz (thenextman)]

The comments for AboutData say

This can be None if /about is the first request made.

Which is true and correct; but is causing a crash in the .NET OpenAPI client if /about is the first request made.

For whatever reason, the .NET OpenAPI generator is not creating a nullable property.

This may be related to the issues I had in #1164, but I don't have time to dig into it now. Since this is non-critical / non-user facing; I just force a value here for the first request (the UNIX epoch seems reasonable).

[github-actions]

Let maintainers know that an action is required on their side

• Add the label release-required Please cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module) when you request a maintainer to cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module)

• Add the label release-blocker Follow-up is required before cutting a new release if a follow-up is required before cutting a new release

• Add the label publish-required Please publish libraries (`Devolutions.Gateway.Utils`, OpenAPI clients, etc) when you request a maintainer to publish libraries (Devolutions.Gateway.Utils, OpenAPI clients, etc.)

• Add the label publish-blocker Follow-up is required before publishing libraries if a follow-up is required before publishing libraries