cli-plugins/hooks: add JSON labels, omitzero

Add labels to define the expected casing and don't serialize
empty fields.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

cli-plugins/hooks/hook_types.go

@@ -1,3 +1,6 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.24
+
 package hooks
 
 // ResponseType is the type of response from the plugin.
@@ -15,18 +18,18 @@ type Request struct {
 	// which is currently being invoked. If a hook for `docker context` is
 	// configured and the user executes `docker context ls`, the plugin will
 	// be invoked with `context`.
-	RootCmd      string
-	Flags        map[string]string
-	CommandError string
+	RootCmd      string            `json:"RootCmd,omitzero"`
+	Flags        map[string]string `json:"Flags,omitzero"`
+	CommandError string            `json:"CommandError,omitzero"`
 }
 
 // Response represents a plugin hook response. Plugins
 // declaring support for CLI hooks need to print a JSON
 // representation of this type when their hook subcommand
 // is invoked.
 type Response struct {
-	Type     ResponseType
-	Template string
+	Type     ResponseType `json:"Type"`
+	Template string       `json:"Template,omitzero"`
 }
 
 // HookType is the type of response from the plugin.