Formatter rewrites quoted reference containing keyword to non-quoted one which fails to parse

[anderseknert]

package p

import rego.v1

foo := data.foo.bar["contains"]("baz")

running opa fmt on this file rewrites the ref:

package p

import rego.v1

foo := data.foo.bar.contains("baz")

which doesn't parse, as contains is of course a keyword

(although, a keyword that is also a built-in function, and shouldn't be considered a keyword at this location, but that's another issue)

[anderseknert]

I guess this is like the third issue we have where the real problem is how keywords can't be used in refs. We should just fix that.