mango: fix $beginsWith range
In the intial implementation of $beginsWith, the range calculation
for json indexes mistakenly appends an integer with the size of
8 bits which gets maxed out at FF, rather than building a binary
with an extra 3 bytes at the end.
This commit fixes the `mango_idx_view:range/5` by correctly appending
the `U+FFFF` code point to create a utf-8 encoded binary. Additionally,
the Erlang `utf8` binary type ensures the result
is a valid utf8 string. If `Arg` is not a utf8 binary, this will
throw a badarg error.
We expect `Arg` strings to be a valid utf8 but, to be safe,
`mango_selector:norm_ops/1` is enhanced to verify
that any argument to `$beginsWith` is a utf8 string.
3 files changed
