fixed missing whitespace in plan() debug logging

When debug logging is enabled, the plan() function logs lines like:

    <previous output>
    Plan: DEBUG: __init__: Creates=13, Updates=0, Deletes=0Existing=0
    <following output>

  Where a space between "Deletes=0" and "Existing=0" is missing.
  This adds it.

pools used as fallbacks should count as seen

Change DNSimple's Provider to query zones instead domains

A quick summary of a problem with have with DNSimple provider:
Let's suppose that I have the following config:

zones:
  30.114.195.in-addr.arpa.:
    sources:
      - config
    targets:
      - dnsimple

Even if a customer has this Reverse zone configured in DNSimple, this
fails with:

400 Bad Request for url: https://api.sandbox.dnsimple.com/v2/x/domains

because it is trying to create a domain because the zone wasn't found.
octodns.provider.dnsimple.DnsimpleClientNotFound: Not found

This happens because the GET /domains endpoint at DNSimple does not
bring Reverse Zones. To make this work nice, we should use /zones/
instead making it return properly the reverse zones.

- implemented HetznerClient API class
- tested manually, lacking formal tests

Capture plan output in File as argument to sync

Co-authored-by: Ross McFarland <ross@github.com>

Co-authored-by: Ross McFarland <ross@github.com>

Change the auth value to have a proper string not a binary rep

Enable NS support for non-root NS records

Bump pyyaml from 5.3.1 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.3.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/5.3.1...5.4)

Signed-off-by: dependabot[bot] <support@github.com>

Update README.md: fix typo

Revert "Stopped running CI for doc changes."

This reverts commit a8366aa02d.

Update branch name

Fix handling of NULL SRV records in Cloudflare and Digital Ocean providers, add warnings to DNS Made Easy and DNSimple providers