can anyone give me an example of: a letter of invitation from reference in Ireland please

im Rumanian and i live in Spain with a residence work permit but i want to move to ireland.my boyfriend is irish and i was thinking to get a holiday visa first then go from there once i am in ireland but i have no idea how a letter of invitation for irelad looks like can anyone give me an example of how my boyfried should whrite the invitation letter for me please?