Reorganize fragments: flat structure from fragments/shared/ and fragments/platform/

fragments/section-data/post/base.ks

@@ -0,0 +1,9 @@
+# Core post-installation configuration
+
+%post --log=/mnt/sysimage/root/post.log # Beginning of the post-installation section. Log all messages to a given file
+
+localectl set-keymap ch-fr # Set keymap to `ch-fr`. Alternatively, `us` can be picked.
+dnf update -y # Update the system
+grub2-mkconfig -o /boot/grub2/grub.cfg # Unsure it is actually useful
+
+%end # End of the %post section

fragments/section-data/post/nochroot.ks

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+# Post-installation no-chroot section
+
+%post --nochroot --log=/mnt/sysimage/root/post-nochroot.log # Beginning of the post-installation section. Log all messages to a given file
+
+%end # End of the %post section

fragments/section-data/post/server.ks

@@ -0,0 +1 @@
+# Server-specific post-install tasks