Select multiple allow methods for rpc shows wrong error

[michalbundyra]

When you edit an RPC service the UI allows me to select multiple allowed methods. But it seems to be imposible to process this. The backend will show the error:
"controller_class: The Controller Class must be a valid, fully qualified, PHP class name" which is a strange error since I didn't change the controller class at all

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Originally posted by @jaapio at zfcampus/zf-apigility-admin#234

[FXLima]

Create a new service RPC in: Api-Tools Laminas

XHRPOSThttp://localhost/api-tools/api/module/myapp/rpc
[HTTP/1.1 422 Unprocessable Entity 10175ms]

validation_messages Object { controller_class: […], accept_whitelist: […], content_type_whitelist: […], … }
controller_class [ "The Controller Class must be a valid, fully qualified, PHP class name" ]
0 "The Controller Class must be a valid, fully qualified, PHP class name"
accept_whitelist [ "The Accept Whitelist must be an array of valid media type expressions" ]
0 "The Accept Whitelist must be an array of valid media type expressions"
content_type_whitelist [ "The Content-Type Whitelist must be an array of valid media type expressions" ]
0 "The Content-Type Whitelist must be an array of valid media type expressions"
http_methods [ "The HTTP Methods must be an array of valid HTTP method names" ]
0 "The HTTP Methods must be an array of valid HTTP method names"
type "http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html"
title "Unprocessable Entity"
status 422
detail "Failed Validation"