Enhance Functions REST API in Web Server

[giancarloromeo]

This issue contains backend changes needed for #1905.

In detail, following endpoints are required and/or need improvements:

• list_functions_with_extras
• get_function_with_extras
• update_function: title or description
• return the readFuctions in functions-permissions

Source:

Needed endpoints in the webserver rest API:

• list_functions_with_extras
• get_function_with_extras
• update_function: title or description
• return the readFuctions in functions-permissions

Function read model:

• Function's:
  • id
  • type
  • title
  • description
  • created
  • modified
  • inputs, outputs, defaults
  • permissions
• Underlaying resource's
  • thumbnail
  • (workbench)
  • (workbench UI)

later:

• delete_function
• update_permissions
• search_function
• list_function + sort

Originally posted by @wvangeit in #1905