New features

• #1801 - Basic support for RFC8738, an extension to ACME that allows servers to issue certificates for IP addresses. They can be input through the Manual and CSR source plugins and validated using tls-alpn or any http method. Installation support for IIS is limited: renewals for ip-only bindings will work after setting up manually for the first time, but the program will not create them automatically yet. Note that this feature can only be used if the ACME service also supports it. So far none of the popular ones do. Brought to our attention by @Virinum.
• #1865 - @marcoskirchner contributed a remote validation plugin, which pushes validation challenge answers to a REST endpoint of your choice. His corresponding server implementation can be used to recieve the answers and forward them to the ACME server, but you could also develop your own. This allows you to run win-acme on a seperate server from the one that recieves traffic from the domain.

Enhancements

• We have decided to rename “target plugins” to “source plugins” because that name makes more sense given their function, which is working at the beginning of the pipeline to provide the rest of steps with list of identifiers (DNS names or IP addresses) to work with. To avoid breaking workflows the
  old command line parameter --target continues to be accepted as an alias for the new --source parameter.
• The previous release added support for secret management in the core program. This release extends that to all extra plugins. To do this properly without duplicating a lot of code the user input subsystem was rewritten, so that will feel a lot more consistent moving forwards, both in the main program and the various plugins. This also makes authoring
  additional plugins easier.
• The parameter --validation-mode is no longer required if there are no naming conflicts between plugins, e.g. instead of --validation-mode dns-01 --validation azure you can now simply use --validation azure because there is no other plugin with that name.
• Add proxy support to the Google Cloud DNS plugin.
• Added basic “Edit renewal” opening in Manage renewals menu, which is basically the same as creating a new renewal (with full options), that overwrites the previously created settings, but maintains history.
• All plugins and the main program are now built with compile-time nullable checking, improving code quality.
• Updated various NuGet packages for latest bug fixes from upstream components.
• Updated local copy of the Public Suffix List for offline installations.
• The Route53 plugin now supports parallel operations, greatly speeding up the validation proces when including multiple domains in a certificate.

Bug fixes

• Configuring a Powershell script in a path with spaces and/or single quotes would fail to run.
• Command line parsing better handles dashes embedded in quoted strings, reported and tested by @wchao.
• #1849 – PemFiles plugin was asking “PFX password”, which was mislabelled, thanks @MarcoMiltenburg!
• #1847 – The published build of the Google Cloud DNS plugin didn’t work with the published build of the main program. This has been corrected. Thanks for noticing @ArcanoxDragon!
• #1831 – The program would crash when providing it with an invalid argument, thanks @johlju for the report!