POST endpoint should allow global parameters

[matteofigus]

Current behaviour for making a request is making a POST to the registry's base url with a payload like

{
  "components": [
    { "name": "component", "parameters": { "domain": "it" }},
    { "name": "component2", "parameters": { "domain": "it", "hello": "world" }}]
}

We want, when multiple component requires the same parameters, to be able to pass this parameters globally. Example (The following example aims to be equivalent to the previous one):

{
  "parameters": { "domain": "it" },
  "components": [
    { "name": "component"},
    { "name": "component2", "parameters": { "hello": "world" }}]
}

Acceptance:

• when a global parameter is specified, it is used by all the components no exclusion
• when a global parameter is specified and component includes the same parameter with different value, the global parameter is overwritten for that component
• when both global and component parameters are specified, both are going to be used (see example for hello parameter)