GitLab

Update to use gitlab-ci-helpers

See merge request !1

`string.sub(k, 8)` in Lua extracts every character from the eight byte
onwards, and not the eight first bytes. Also, `x-feide` is 7 bytes,
not 8. The result is that we only delete headers named something like
`???????X-Feide`.

This patch fixes this bug by correcting the `sub()`-call, and adding
the trailing `-` to the header name, bringing the length to 8
characters.

We need to use an exact match for our various URL handlers, so that we
do not inadvertently grab requests that were not targeted at us.

Also gets rid of the need for a server_name variable

This is useful to avoid problems related to attribute names with colon in them, or attribute values with comma in them etc