Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

internal/component/component.go

@@ -0,0 +1,69 @@
+// Package component holds the main abstraction for components.
+package component
+
+import (
+	"github.com/FAU-CDI/wisski-distillery/internal/config"
+)
+
+// Component represents a logical subsystem of the distillery.
+//
+// By convention these are defined within their corresponding subpackage.
+// This subpackage also contains all required resources.
+// Furthermore, a component is typically instantiated using a call on the ["distillery.Distillery"] struct.
+//
+// Each Component should make use of [ComponentBase] for sane defaults.
+//
+// For example, the web.Web component lives in the web package and can be created like:
+//
+//	var dis Distillery
+//  web := dis.Web()
+type Component interface {
+	// Name returns the name of this component.
+	// It should correspond to the appropriate subpackage.
+	Name() string
+
+	// Path returns the path this component is installed at.
+	// By convention it is /var/www/deploy/internal/core/${Name()}
+	Path() string
+
+	// Stack can be used to gain access to the "docker compose" stack.
+	//
+	// This should internally call
+	Stack() Installable
+
+	// Context returns a new InstallationContext to be used during installation from the command line.
+	// Typically this should just pass through the parent, but might perform other tasks.
+	Context(parent InstallationContext) InstallationContext
+
+	// Base() returns a reference to a base component
+	// This is implemented by an embedding on ComponentBase
+	Base() *ComponentBase
+}
+
+// ComponentBase implements base functionality for a component
+type ComponentBase struct {
+	Dir string // Dir is the directory this component lives in
+
+	Config *config.Config // Config is the configuration of the underlying distillery
+}
+
+// Base returns a reference to the ComponentBase
+func (cb *ComponentBase) Base() *ComponentBase {
+	return cb
+}
+
+// Path returns the path to this component
+func (cb ComponentBase) Path() string {
+	return cb.Dir
+}
+
+// Context passes through the parent context
+func (ComponentBase) Context(parent InstallationContext) InstallationContext {
+	return parent
+}
+
+// MakeStack registers the Installable as a stack
+func (cb ComponentBase) MakeStack(stack Installable) Installable {
+	stack.Dir = cb.Dir
+	return stack
+}