Change DomainFilter to apply to records as well

[bl1nk]

These changes were implemented for the setup mentioned in #1137:

We start multiple external-dns processes, one for each Hosted Zone where DNS entries should be created (other options omitted for brevity):
1: external-dns --domain-filter=cluster1.example.com
2: external-dns --domain-filter=example.com --exclude-domains=cluster1.example.com
Process "1" does exactly what it is supposed to, creating records in the Hosted Zone cluster1.example.com only.
Process "2" however tries to create DNS entries for example.com and cluster1.example.com:
[...]

domain_filter.go was moved to the endpoint package to make it possible to filter and exclude record names in plan.filterRecordsForPlan() so it does not have to be implemented in every single provider. Now Process "2" will only create DNS entries for example.com. Before --exclude-domains was only filtering/excluding DNS zones.

Because some providers access DomainFilter.filters directly it had to be exported.

A build with these changes has been running in production at FREE NOW for a couple of weeks without issues.

Fixes #1137

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[alexanderbuhler]

@bl1nk Highly appreciated change! Do you have a public docker image containing these changes somewhere?

[bl1nk]

@bl1nk Highly appreciated change! Do you have a public docker image containing these changes somewhere?

@alexanderbuhler Unfortunately not. With the only requirement being Docker installed and running you can clone the repo, check out my branch and run IMAGE=your-registry/external-dns make build.mini to build your own image though.

[njuettner]

/lgtm

[linki]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bl1nk, linki

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[linki]

@bl1nk Thank you!