Add the ability to configure sign nodes to only sign specific products

[javihernandez]

In order to provide a more granular configuration and ensure that community products don't interfere with AlmaLinux building, we need to add the ability in sign nodes to only sign specific products using a configuration option.

AC:

• A sign node will sign packages it is allowed to sign via the configuration option
• A sign node will reject signing packages that do not belong to the allowed products