[fsresizer] Add setting required

- If resize is required, fail if it doesn't happen.

src/modules/fsresizer/ResizeFSJob.cpp

@@ -33,6 +33,7 @@
 #include "JobQueue.h"
 #include "GlobalStorage.h"
 
+#include "utils/CalamaresUtils.h"
 #include "utils/Logger.h"
 #include "utils/Units.h"
 
@@ -113,6 +114,7 @@ ResizeFSJob::RelativeSize::apply( Device* d )
 
 ResizeFSJob::ResizeFSJob( QObject* parent )
     : Calamares::CppJob( parent )
+    , m_required( false )
 {
 }
 
@@ -334,6 +336,8 @@ ResizeFSJob::setConfigurationMap( const QVariantMap& configurationMap )
 
     m_size = RelativeSize( configurationMap["size"].toString() );
     m_atleast = RelativeSize( configurationMap["atleast"].toString() );
+
+    m_required = CalamaresUtils::getBool( configurationMap, "required", false );
 }
 
 CALAMARES_PLUGIN_FACTORY_DEFINITION( ResizeFSJobFactory, registerPlugin<ResizeFSJob>(); )

src/modules/fsresizer/ResizeFSJob.h

@@ -107,6 +107,7 @@ private:
     RelativeSize m_atleast;
     QString m_fsname;  // Either this, or devicename, is set, not both
     QString m_devicename;
+    bool m_required;
 
     using PartitionMatch = QPair<Device*, Partition*>;
     /** @brief Find the configured FS using KPMCore @p backend */

src/modules/fsresizer/fsresizer.conf

@@ -33,5 +33,17 @@ size: 100%
 # size, as above. If missing, then it's assumed to be 0,
 # which means resizing is always worthwhile.
 #
+# If *atleast* is not zero, then the setting *required*,
+# below, becomes relevant.
+#
 # Percentages apply to **total device size**.
-atleast: 1000MiB
+#atleast: 1000MiB
+
+# When *atleast* is not zero, then the resize may be
+# recommended (the default) or **required**. If the
+# resize is required and cannot be carried out (because
+# there's not enough space), then that is a fatal
+# error for the installer. By default, resize is only
+# recommended and it is not an error for no resize to be
+# carried out.
+required: false