osbuild2: separate input base types into new file

Keep input base types / interfaces separately from stages for
readability.
Cleaned up some unused interfaces in the process.

internal/osbuild2/input.go

@@ -0,0 +1,26 @@
+package osbuild2
+
+// Collection of Inputs for a Stage
+type Inputs interface {
+	isStageInputs()
+}
+
+// Single Input for a Stage
+type Input interface {
+	isInput()
+}
+
+// Fields shared between all Input types (should be embedded in each instance)
+type inputCommon struct {
+	Type string `json:"type"`
+	// Origin should be either 'org.osbuild.source' or 'org.osbuild.pipeline'
+	Origin string `json:"origin"`
+}
+
+type StageInput interface {
+	isStageInput()
+}
+
+type References interface {
+	isReferences()
+}

internal/osbuild2/stage.go

@@ -18,41 +18,11 @@ type Stage struct {
 	Mounts  Mounts       `json:"mounts,omitempty"`
 }
 
-// Collection of Inputs for a Stage
-type Inputs interface {
-	isStageInputs()
-}
-
-// Single Input for a Stage
-type Input interface {
-	isInput()
-}
-
-// Fields shared between all Input types (should be embedded in each instance)
-type inputCommon struct {
-	Type string `json:"type"`
-	// Origin should be either 'org.osbuild.source' or 'org.osbuild.pipeline'
-	Origin string `json:"origin"`
-
-	// References References `json:"references"`
-}
-
-type StageInput interface {
-	isStageInput()
-}
-
-type References interface {
-	isReferences()
-}
-
 // StageOptions specify the operations of a given stage-type.
 type StageOptions interface {
 	isStageOptions()
 }
 
-type InputOptions interface {
-}
-
 type rawStage struct {
 	Type    string          `json:"type"`
 	Options json.RawMessage `json:"options"`