Registered query: presence flags for input URL parameter

[lukas-vlcek]

Add presence flag for each valid URL parameter. This will allow better possibilities when doing Mustache scripting.

For example if input parameters will be:

{
    "foo": ["one, "two", "three"],
    "bar": 1
}

Then for each key we will add a boolean flag (is_*) like this:

{
    "foo": ["one, "two", "three"],
    "is_foo": true,
    "bar": 1,
    "is_bar": true
}

[unibrew]

Very good idea :)

[lukas-vlcek]

Working around Mustache weakness :-)