Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

When `URI.escape` was deprecated, we switched to using `CGI.escape` to
construct the request path in push.rb.

The problem with that is that it mishandles spaces, encoding them as `+`
rather than `%20`. This leads to literal `+` characters in metric
labels, which is a bug.

This commit uses `ERB::Util.url_encode` instead, which gives us the
behaviour we want.

It's not the part of the standard library I expected to use for this,
but it's the only one that seems to have the behaviour we want and that
hasn't disappeared in Ruby 3.0. `WEBrick::HTTPUtils.escape` seems
similar on the surface, but doesn't encode `&`. Presumably it's intended
as a best-effort way to encode an entire URL, and has to assume that any
`&` character is a separator between query params.

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>