Hi valdir.marcos,
Thanks for the links, I've went through these threads you suggested and actually - there are even more questions than answers for me after reading them. Maybe I will try to explain more what is on my mind and what is my experience so far.
I have experience with REST, but not with Delphi (or Lazarus). I have couple of years of experience with Delphi, but it was a couple of years ago when I've moved to Java, and then went to some cloud platform development. As for Lazarus - I've made a mid-sized project in Lazarus couple of months ago, but it was not related to REST, or even not related to networking at all, just a plain desktop app. So I have never created an app that would do similar things in Delphi or Lazarus. Therefore, as you can see, I'm not a noob when it comes to REST, JSON etc, however, I've only implemented such code (both clients and servers) with technologies other than Lazarus/FPC.
What I need to have (and what I don't need):
1. I only need to have REST client (I don't need the server, at least that's what I think right now).
2. I want to avoid the steep learning curve that some of the suggested component packages have. Most preferably, I'd like to use the standard component/packages/units if possible.
3. I want to be able to connect to a REST endpoint (HTTPS support is required).
4. I want to be able to easily manage the HTTP headers (to pass credentials, session Ids, security tokens etc depending on the cloud service provider security settings).
5. I want to be able to pull the data, preferably in a bulk approach (it is supported by the REST service).
6. For all of the the above - I think can it can be even done via simple HTTP(S) request. But maybe there is some simple wrapper library?
7. I want to be able to deserialize JSON (or SOAP) content from HTTP REST response of the source endpoint. But it should be done with some kind of abstract approach, because there is no fixed data structure. This means I don't need any ORM, because I think that there is no option to persist the results from the source endpoint in any temporary (local or remote) database. I only need to push it into the twin REST destination endpoint. Most probably I would store the parts of the JSON/SOAP responses representing individual records (or record batches) in a text files, because I will upload them into the destination REST endpoint using the very same format.
I'm not very familiar with the "standard" units/components provided with FPC/Lazarus (I mean these related to networking, JSON, etc.).
I'm looking forward to some hints what to pick or where to look for being able to do the implementation of a simple proof of concept.
And, BTW, I don't speak Portuguese or Spanish. English only (and Polish as my first language).