How to mount and use swap partition _only_ for hibernation ?

Question

By "hibernation" I mean suspend to disk.
My disk is a bit poor in RAM and the dirsk is slow, so I want to prevent any swap use of my system.
AND I want to use hibernation, in order to boot fatser... and not to loose my workspace state.
With a swap partition, hibernation works nicely.
But any intensive web browser easily lealds to incresed memory usage, hence swap use.
I have lowered the swap priority in /etc/fstab, down to 1 (and even tried 0).
Still, I am not satisfied : If would like not to use swap at all but for hibernation.
My plan was hence :
1) disable the automatic swap mount at boot
2) add a systemd unit to only moutn before hibernation
The first part was easy : I added a "noauto" option in /etc/fstab. Great, no more mounted swap. But, as expected, no more successful hibernation.
Then I tried to create a custom systemd unit.
- first copy the unit file automatically generated by systemd in /run/systemd/generator/dev-....swap to /etc/systemd/system/
- and add "Before=sleep.target" line in the Unit section
Result file here :
> cat /etc/systemd/system/dev-disk-by\x2duuid-blablablabla.swap
[Unit]
Description=Swap required for hibernation
Before=sleep.target
[Swap]
What=/dev/disk/by-uuid/blablablablabla
Priority=5
>
Next step show be to enable it, but I first run a safety check :
> systemctl show dev-disk-by\x2duuid-blablablabla.swap
Id=dev-disk-by\x2duuid-blablablabla.swap
Names=dev-disk-by\x2duuid-blablablabla.swap
Requires=-.mount
Wants=system.slice
BindsTo=dev-disk-by\x2duuid-blablablabla.device
RequiredBy=swap.target
WantedBy=dev-disk-by\x2duuid-blablablabla.device
Conflicts=umount.target
Before=sleep.target umount.target swap.target
After=systemd-journald.socket dev-disk-by\x2duuid-blablablabla.device system.slice -.mount
RequiresMountsFor=/dev/disk/by-uuid/blablablabla
Description=Swap required for hibernation
LoadState=loaded
ActiveState=inactive
SubState=dead
FragmentPath=/etc/systemd/system/dev-disk-by\x2duuid-blablablabla.swap
UnitFileState=static
InactiveExitTimestampMonotonic=0
ActiveEnterTimestampMonotonic=0
ActiveExitTimestampMonotonic=0
InactiveEnterTimestampMonotonic=0
CanStart=yes
CanStop=yes
CanReload=no
CanIsolate=no
StopWhenUnneeded=no
RefuseManualStart=no
RefuseManualStop=no
AllowIsolate=no
DefaultDependencies=yes
>
The problem here is that, somehow, a RequiredBy=swap.target line is apaprently automatically added, and makes exactly NOT what I want.
I've been battling a bit with systemd, but so far I have no clue how to do this correctly.
Important : I wand a clean "official" way, not to do a "service" unit that calls an home-brewed script taht calls swapon. I can do that, but systemd should be able to do it better than me, and without any trick.

Answer 1

Hello and thank you all
@fdservices & @WonderWoofy :
In fact, I forgot to mentionned swappiness, just tought about mentionneing the swap priority which act at a very different level is only revelevant when you ahve several swap files.
I have already modified that setting since quite a long time... and it indeed makes the system behaviour so much better.
Honestly, I could do with it... that's what I am doing since a few months in fact, and it really largely improved the user experience.
Still, the setting only makes swapping unlikely, but does not forbid it.
@WonderWoofy & @lucke :
You may be right, I could satisfy with swapiness...
Still, my feeling is that swap at run-time is mostly a remeniscence of the time where having several megabytes of RAM was juste a fantasm. At that time, at least for some intensive operations, simulating more RAM thansk to the cheaper & slower disk capacity was really decisive for a good user experience... and to allow some operations like some huge compilations. My feeling is that today, with our Gigabytes of RAM on our desktop/laptop, the need is much lower. In fact a swap is probably counter-productive for SSD for example (fast, yes, but swap is by nature something you write quite often, reducing teh SSD lifetime significantly). And simulating extra RAM is also counter-productive with applications such as web browsers which handle large amount of memory to handle cache themselves; it causes memory pressure, hence trigger swapping and machien slowdown instead of trigerring their pseudo-smart memory cleaning mechanisms. Last but not least, it does not encourage any improvement on application memory needs and rationalisation.
In fact, unless when I compile huge programs, or on really-limited-memory (embedded) systems, or eventually if swap can be hosted on significantly faster-than-storage disks, I feel that swapping does not really improve the user experience and system performance... and in contrary reduces them by having to handle swapping on and off memory & cache pages.
SO that's why I want to try. It's OK if I fail, swappinees fixes most my user experience issue, but I try to solve my more "theorical" issue as well.
And honestly, it is also to lean & play a bit with systemd as well.
More to come, I have things partially working now. Partially for now, and maybe perfectly with your help ?