These seem to be the common pin numbers, this shows the relay in it's normal or un-energised state.
Some eBay warning buzzers seem to have a buzzer included in a relay case, there are others which look like your original one with something (probably a diode) under heat shrink sleeve on one of the wires.
I had a quick look but the wire that carries the 'key inserted' signal and illuminates the dashboard witness light does not seem very accessible without dismantling quite a lot of plastic trim; just going for door open + lights on as discussed above seems the way to go unless anyone can figure a simple way to switch when there is a lack of 12V (Ign key off or out).
The relay will energise across 85 & 86 fed from the lights and grounded via the door. The light power also feeds the buzzer through common pin 30 out through N/O pin 87.
No lights = no power to energise or buzz
Door shut = no ground path to close the relay
Just to add to confusion, discovered this variation but I'm not convinced the light switch is in the right place in the diagram, they're usually on the ground side:
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TG