(chocolatey#1144) Add usePackageHashValidation feature

This feature is used to control if the checksum of the downloaded
.nupkg is checked against the checksum provided by the package
source. It is disabled by default, as it unknown if it works
correctly with all major NuGet v2 implementations.

src/chocolatey/infrastructure.app/ApplicationParameters.cs

@@ -238,6 +238,7 @@ public static class Features
             public static readonly string LogValidationResultsOnWarnings = "logValidationResultsOnWarnings";
             public static readonly string UsePackageRepositoryOptimizations = "usePackageRepositoryOptimizations";
             public static readonly string DisableCompatibilityChecks = "disableCompatibilityChecks";
+            public static readonly string UsePackageHashValidation = "usePackageHashValidation";
         }
 
         public static class Messages

src/chocolatey/infrastructure.app/builders/ConfigurationBuilder.cs

@@ -338,6 +338,7 @@ private static void SetAllFeatureFlags(ChocolateyConfiguration config, ConfigFil
             config.Features.LogWithoutColor = SetFeatureFlag(ApplicationParameters.Features.LogWithoutColor, configFileSettings, defaultEnabled: false, description: "Log without color - Do not show colorization in logging output.");
             config.Features.LogValidationResultsOnWarnings = SetFeatureFlag(ApplicationParameters.Features.LogValidationResultsOnWarnings, configFileSettings, defaultEnabled: true, description: "Log validation results on warnings - Should the validation results be logged if there are warnings?");
             config.Features.UsePackageRepositoryOptimizations = SetFeatureFlag(ApplicationParameters.Features.UsePackageRepositoryOptimizations, configFileSettings, defaultEnabled: true, description: "Use Package Repository Optimizations - Turn on optimizations for reducing bandwidth with repository queries during package install/upgrade/outdated operations. Should generally be left enabled, unless a repository needs to support older methods of query. When disabled, this makes queries similar to the way they were done in earlier versions of Chocolatey.");
+            config.Features.UsePackageHashValidation = SetFeatureFlag(ApplicationParameters.Features.UsePackageHashValidation, configFileSettings, defaultEnabled: false, description: "Use Package Hash Validation - Check the hash of the downloaded package file against the source provided hash. Only supports sources that provide SHA512 hashes. Disabled by default. Available in 2.3.0+");
             config.PromptForConfirmation = !SetFeatureFlag(ApplicationParameters.Features.AllowGlobalConfirmation, configFileSettings, defaultEnabled: false, description: "Prompt for confirmation in scripts or bypass.");
             config.DisableCompatibilityChecks = SetFeatureFlag(ApplicationParameters.Features.DisableCompatibilityChecks, configFileSettings, defaultEnabled: false, description: "Disable Compatibility Checks - Disable showing a warning when there is an incompatibility between Chocolatey CLI and Chocolatey Licensed Extension. Available in 1.1.0+");
         }

src/chocolatey/infrastructure.app/configuration/ChocolateyConfiguration.cs

@@ -561,6 +561,7 @@ public sealed class FeaturesConfiguration
         public bool ExitOnRebootDetected { get; set; }
         public bool LogValidationResultsOnWarnings { get; set; }
         public bool UsePackageRepositoryOptimizations { get; set; }
+        public bool UsePackageHashValidation { get; set; }
     }
 
     //todo: #2565 retrofit other command configs this way