hello there ^^ I'm delphi doftware developer ^^
I used to deal with delphi since version 7 till 10.3 Rio using both VCL and FMX libraries , well i used to deal with REST services in delphi using either REST components like TRESTCLIENT , TRESTREQUEST and TRESTRESPONSE where it supports all REST methods like POST,PUT,DELETE,GET , or INDY or other third party , dealing with both JSON and XML for REQUEST/RESPONSE , I have already made an application that uses REST you can check in my portfolio called 4tix ^^
just provide me with more info and I will do my best
best regards