What should be the electrical wiring diagram?

Question

Do it yourself

The following equipment is available:
1) Filter pump (voltage: 220 V, power consumption: 1.05 kW)
2) Electric heater (voltage: 220 V, power consumption: 3.4 kW)
3) Air massage (voltage: 220 V, power consumption: power: 0.75 kW)
4) Backlight (voltage: 220 V, power consumption: 15 W)
I would like to implement the circuit so that it is impossible to turn on the electric heater without turning on the filter pump, but it is possible to turn on the filter pump without turning on the electric heater filter washing). Aeromassage and lighting can be connected to separate machines (without much reference to the operation of the filter pump).
An RCD is installed at the input (at 32A if I'm not mistaken).
Considered the following options:
1) PLC (PLC?) or something similar (Intel Galileo gen2 and MSP430 LaunchPad Texas Instruments are available)
2) A circuit with a coil through which to determine whether the filter pump is turned on or not.
3) Scheme with the installation of sensors / flow sensors / water.
4) A circuit with an ON-OFF-ON switch and two contactors (electromagnetic starters?). In which in mode 1 both contactors are switched on and the filter pump works together with the heater, and in mode 2 only the filter pump works.
5) A scheme in which the inclusion of an automatic machine supplying voltage to the heater is mechanically impossible until the corresponding automatic filter pump is turned on.
Help me choose (invent?) the optimal connection scheme and select the necessary components (especially in terms of current strength). According to the strength of the current, I assume so
3.5kW=>16A
1.05kW=>6A
0.75kW=>6A
A for 15W? 1A?
Thanks in advance.
PS In the future, I plan to automate the work scheme by implementing the script for turning on the backlight and air massage at the entrance to the room, as well as turning on the electric heater and filter pump at the right time (for example, via a PC).