[libcalamares] Define interface for Module descriptor

- add fields -- all const, all bogus -- to the descriptor,
  introduce a stub method to load the descriptor from
  YAML data (e.g. read from module.desc)
- lighten the type-naming in Module a little, with usings

src/libcalamares/modulesystem/Descriptor.cpp

@@ -7,6 +7,8 @@
 
 #include "Descriptor.h"
 
+#include "utils/Logger.h"
+
 namespace Calamares
 {
 namespace ModuleSystem
@@ -44,5 +46,17 @@ interfaceNames()
     return table;
 }
 
+Descriptor::Descriptor() {}
+
+Descriptor
+Descriptor::fromDescriptorData( const QVariantMap& moduleDesc )
+{
+    Descriptor d;
+
+    cDebug() << moduleDesc;
+
+    return d;
+}
+
 }  // namespace ModuleSystem
 }  // namespace Calamares

src/libcalamares/modulesystem/Descriptor.h

@@ -61,17 +61,65 @@ const NamedEnumTable< Interface >& interfaceNames();
  * to create a more strongly-typed Module Descriptor that carries
  * only the necessary information and no variants.
  */
-// using Descriptor = QVariantMap;
-
 class Descriptor
 {
 public:
+    ///@brief an invalid, and empty, descriptor
     Descriptor();
 
+    /** @brief Fills a descriptor from the loaded (YAML) data.
+     *
+     */
+    static Descriptor fromDescriptorData( const QVariantMap& moduleDesc );
+
     bool isValid() const { return false; }
 
     QString name() const { return QString(); }
+    Type type() const { return Type::Job; }
+    Interface interface() const { return Interface::QtPlugin; }
+
     bool isEmergency() const { return false; }
+    bool hasConfig() const { return true; }
+
+    /// @brief The directory where the module.desc lives
+    QString directory() const { return m_directory; }
+    void setDirectory( const QString& d ) { m_directory = d; }
+
+    QStringList requiredModules() const { return QStringList {}; }
+
+    /** @section C++ Modules
+     *
+     * The C++ modules are the most general, and are loaded as
+     * a shared library after which a suitable factory creates
+     * objects from them.
+     */
+
+    /// @brief Short path to the shared-library; no extension.
+    QString load() const { return QString(); }
+
+    /** @section Process Job modules
+     *
+     * Process Jobs are somewhat deprecated in favor of shellprocess
+     * and contextualprocess jobs, since those handle multiple configuration
+     * much more gracefully.
+     *
+     * Process Jobs execute one command.
+     */
+    /// @brief The command to execute; passed to the shell
+    QString command() const { return QString(); }
+    /// @brief Timeout in seconds
+    int timeout() const { return 30; }
+    /// @brief Run command in chroot?
+    bool chroot() const { return false; }
+
+    /** @section Python Job modules
+     *
+     * Python job modules have one specific script to load and run.
+     */
+    QString script() const { return QString(); }
+
+private:
+    QString m_directory;
 };
 
 }  // namespace ModuleSystem

src/libcalamares/modulesystem/Module.h

@@ -51,6 +51,9 @@ Module* moduleFromDescriptor( const ModuleSystem::Descriptor& moduleDescriptor,
 class DLLEXPORT Module
 {
 public:
+    using Type = ModuleSystem::Type;
+    using Interface = ModuleSystem::Interface;
+
     virtual ~Module();
 
     /**
@@ -132,13 +135,13 @@ public:
      * @brief type returns the Type of this module object.
      * @return the type enum value.
      */
-    virtual ModuleSystem::Type type() const = 0;
+    virtual Type type() const = 0;
 
     /**
      * @brief interface the Interface used by this module.
      * @return the interface enum value.
      */
-    virtual ModuleSystem::Interface interface() const = 0;
+    virtual Interface interface() const = 0;
 
     /**
      * @brief Check the requirements of this module.