For general approaches check Debugging Web articles: Part 1, Part 2.

Check this post to see how you can access all levels of dynamic object.

I suggest you contact the WRC for this problem.

I think the problem is in the command escaping.

Try

C:\InterSystems\Cache\bin\cache.exe -s C:\InterSystems\Cache\mgr -U %%SYS C:\Users\Zdenda\Desktop\run.script 

Well, show your cmd script (as text) and ObjectScript script.

ObjectScript script I guess. Just a file with ObjectScript commands.

Here's a sample.

You need to either escape your command or use a separate file for a script. I recommend a file.

I've got minimal security settings

Then you don't need to provide user and password.

  I can use this method right Login(Username As %String, Password As %String)?

No. First line of script - user, second line - password. After that - ObjectScript.

Do $system.OBJ.Load("Installer.xml", "c") I dont know why. 

Try full path. Also this method returns status, check it:

Set sc =  $system.OBJ.Load("/path/to/Installer.xml", "c")
Write:('sc) $System.Status.GetErrorText(sc) 

First two lines of your script should probably be user and password, unless you're running a minimal security install or enabled OS authentication.

ObjectScript code after that, yes, sothis looks correct

do ##class(User.Installer).setup()  

Maybe you need to load User.Installer beforehand?

Use $system.OBJ.Load(file, "c") to load and compile class(es) you need.

Sure

csession {INSTANCE} -U{NAMESPACE} < {SCRIPT}

Script contains code you want to execute, in your case the call to installer manifest. It could be a file or just the code itself.

Example.

A series of articles about automating CI/CD.

Fixed some issues in REST, but you have license problem.

ClassMethod CreateCoffee() As %Status
{

s json = {}.%FromJSON(%request.Data)
s CoffeeProp = ##class(User.PropertyName).%New()
s CoffeeProp.CoffeeName= json.CoffeeName
s CoffeeProp.CoffeeColor=json.CoffeeColor
s CoffeeProp.CoffeePrice= json.CoffeePrice
s Status = CoffeeProp.%Save()
}

How is it valid JSON?

1. JSON accepts only double quotes. Single quotes are not valid.

2. Property names must be quoted (in double quotes). error/txt are not quoted.

Here's JSON standard.

Well, maybe it's a handwritten response?

I'd recommend contacting the API developer and verifying that API responses would be indeed JSON.

Can you make the same call to the API using Postman and show the response?

It's very strange that API returns non-json response.

Does my code snippet throw the same error?

You can simplify your code to this:

set dynObj = {}.%FromJSON(objHttpResponse.Data)
set iter = dynObj.%GetIterator()
while iter.%GetNext(.key , .value )  {
       write "key = "_key_" , value = "_value,!

}

Also json is a string so in your code sample it won't have %FromJSON method.

Variables are local to the process.

1.Variables are defined or referenced via <var>, yes, but you can pass the values to the Installer from your script. For example, check MDX2JSON installer:

Set pVars("User")="web"
Set pVars("Password")="dsweb"
Set pVars("Namespace")="TEMP3"
Set pVars("Import")=1
Set pVars("SourceDir")="C:\temp\MDX2JSON\MDX2JSON"
Do ##class(MDX2JSON.Installer).setup(.pVars)

2. You set environment variable in cmd (Windows):

set NEWVAR=SOMETHING

And after that you can get it from installer with:

$system.Util.GetEnviron("NEWVAR")

They go through your web server (i.e. Apache, NodeJS, IIS) directly.

You can serve files via REST, from files or XDatas. Here's an example in WebTerminal app, but it can be generalized to server arbitrary files from FS.

That would work only in the cases where original reference to OREF exists, right?

i was able to convert the HttpResponse.Data to String and than to the Dynamic Object

You don't need to convert to string, pass stream to FromJSON method and it would work.

send a JSON data to a REST API.

Set tAge = 23
Set pRequest= {"name":"abcdefghi","salary":123,"age":(tAge) }

What version are you on? If 2016.2+ then you can convert JSON stream to dynamic object via:

set dynObj = {}.%FromJSON(req.HttpResponse.Data)