Add a new function for converting a CreateConfig

Right now, there are two major API calls necessary to turn a
filled-in CreateConfig into the options and OCI spec necessary to
make a libpod Container. I'm intending on refactoring both of
these extensively to unify a few things, so make a common
frontend to both that will prevent API changes from leaking out
of the package.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

pkg/spec/containerconfig.go

@@ -0,0 +1,22 @@
+package createconfig
+
+import (
+	"github.com/containers/libpod/libpod"
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+// MakeContainerConfig generates all configuration necessary to start a
+// container with libpod from a completed CreateConfig struct.
+func (config *CreateConfig) MakeContainerConfig(runtime *libpod.Runtime, pod *libpod.Pod) (*spec.Spec, []libpod.CtrCreateOption, error) {
+	runtimeSpec, err := config.createConfigToOCISpec()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	options, err := config.getContainerCreateOptions(runtime, pod)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return runtimeSpec, options, nil
+}