weldr: split blueprint into its own package

This will contain all the translation logic from blueprints to pipelines,
which will constitute the main part of composer, so let's separate that
out from the API.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/blueprint/blueprint.go

@@ -0,0 +1,28 @@
+// Package blueprint contains primitives for representing weldr blueprints and
+// translating them to OSBuild pipelines
+package blueprint
+
+import "osbuild-composer/internal/pipeline"
+
+// A Blueprint is a high-level description of an image.
+type Blueprint struct {
+	Name        string    `json:"name"`
+	Description string    `json:"description"`
+	Version     string    `json:"version,omitempty"`
+	Packages    []Package `json:"packages"`
+	Modules     []Package `json:"modules"`
+	Groups      []Package `json:"groups"`
+}
+
+// A Package specifies an RPM package.
+type Package struct {
+	Name    string `json:"name"`
+	Version string `json:"version,omitempty"`
+}
+
+// TranslateToPipeline converts the blueprint to a pipeline for a given output format.
+func (b *Blueprint) TranslateToPipeline(outputFormat string) *pipeline.Pipeline {
+	p := &pipeline.Pipeline{}
+	p.SetAssembler(pipeline.NewTarAssembler(pipeline.NewTarAssemblerOptions("image.tar")))
+	return p
+}