* fix(dnsprovider): do not always initialize each DNS provider

* fix(dnsprovider): fix unnecessary error return value

* ref(dnsprovider): drop the store and use a simple switch for lookup

* docs(tutorials): add tutorial on how to use external-dns with GKE

* docs(gke): document how to setup a zone with its parent

* fix(ingress): append trailing dot to hostnames

* fix(source): update tests for sanitized DNS names

* feat(source): promote MockSource to source package

* feat(source): add MultiSource to merge other Sources

* feat(source): make structs and members of multiSource private

* ref(source): use constructor methods to create sources

* fix: import and use missing package

* fix(source): fix merge conflict with master branch

* storage proposal v1

* few fixes, remove code

* link issues

* another caveat

* fix typos, more details

* small refactoring

Add tests for Google DNS provider

push image tagged with commit sha

add missing certificates to container image

* chore: build docker image with google container builder

* chore: add boilerplate header

* docs: update Readme with example usage

* docs: emphasize the fact that external-dns removes records

* ref(dnsprovider): refactor Google DNSProvider to cleaner

* ref(dnsprovider): make record transformations more efficient

* fix(dnsprovider): document that page processing is thread-safe

* in-memory dnsprovider implementation without tests

* InMemory->InMemoryProvider

* fix checks for batch change validitiy

* fix tests

* gofmt inmemory_test

* improve test coverage

* gofmt inmemory_test

use alpha annotations

route53: initial implementation of Route53 DNS provider

add once flag to exit loop after first sync

allow passing a namespace that limits found resources