feat: add basic ManagedPackPage classes

The idea is to have a base class that defines common behavior, and
subclasses for each modpack provider, adding specific behavior.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/ui/pages/instance/ManagedPackPage.h

@@ -0,0 +1,98 @@
+#pragma once
+
+#include "BaseInstance.h"
+
+#include "modplatform/modrinth/ModrinthAPI.h"
+#include "modplatform/modrinth/ModrinthPackManifest.h"
+
+#include "ui/pages/BasePage.h"
+
+#include <QWidget>
+
+namespace Ui {
+class ManagedPackPage;
+}
+
+class ManagedPackPage : public QWidget, public BasePage {
+    Q_OBJECT
+
+   public:
+    inline static ManagedPackPage* createPage(BaseInstance* inst, QWidget* parent = nullptr)
+    {
+        return ManagedPackPage::createPage(inst, inst->getManagedPackType(), parent);
+    }
+
+    static ManagedPackPage* createPage(BaseInstance* inst, QString type, QWidget* parent = nullptr);
+    ~ManagedPackPage() override;
+
+    [[nodiscard]] QString displayName() const override;
+    [[nodiscard]] QIcon icon() const override;
+    [[nodiscard]] QString helpPage() const override;
+    [[nodiscard]] QString id() const override { return "managed_pack"; }
+    [[nodiscard]] bool shouldDisplay() const override;
+
+    void openedImpl() override;
+
+    bool apply() override { return true; }
+    void retranslate() override;
+
+    /** Gets the necessary information about the managed pack, such as
+     *  available versions*/
+    virtual void parseManagedPack() {};
+
+    /** URL of the managed pack.
+     *  Not the version-specific one.
+     */
+    [[nodiscard]] virtual QString url() const { return {}; };
+
+   public slots:
+    /** Gets the current version selection and update the changelog.
+     */
+    virtual void suggestVersion() {};
+
+   protected:
+    ManagedPackPage(BaseInstance* inst, QWidget* parent = nullptr);
+
+   protected:
+    Ui::ManagedPackPage* ui;
+    BaseInstance* m_inst;
+
+    bool m_loaded = false;
+};
+
+/** Simple page for when we aren't a managed pack. */
+class GenericManagedPackPage final : public ManagedPackPage {
+    Q_OBJECT
+
+   public:
+    GenericManagedPackPage(BaseInstance* inst, QWidget* parent = nullptr) : ManagedPackPage(inst, parent) {}
+    ~GenericManagedPackPage() override = default;
+};
+
+class ModrinthManagedPackPage final : public ManagedPackPage {
+    Q_OBJECT
+
+   public:
+    ModrinthManagedPackPage(BaseInstance* inst, QWidget* parent = nullptr);
+    ~ModrinthManagedPackPage() override = default;
+
+    void parseManagedPack() override;
+    [[nodiscard]] QString url() const override;
+
+   public slots:
+    void suggestVersion() override;
+};
+
+class FlameManagedPackPage final : public ManagedPackPage {
+    Q_OBJECT
+
+   public:
+    FlameManagedPackPage(BaseInstance* inst, QWidget* parent = nullptr);
+    ~FlameManagedPackPage() override = default;
+
+    void parseManagedPack() override;
+    [[nodiscard]] QString url() const override;
+
+   public slots:
+    void suggestVersion() override;
+};