AWS Route 53 provider: fix various problems with handling of alias records

Add pod source [kops compatibility]

Add seanmalloy As Reviewer

Add regex domain filters

Document annotation-filter usage

Avoid nil pointer deference in extractHeadlessEndpoints

Add 'bluecat' as possible option to the provider flag

'bluecat' was missing from the enumerated list of possible values for the provider flag

Pod source is a key feature of kOps' DNS Controller.
Among other things, i is used for etcd and API discovery.

Update to Go 1.16

Co-authored-by: Nick Jüttner <nick@juni.io>

Co-authored-by: Nick Jüttner <nick@juni.io>

Co-authored-by: Nick Jüttner <nick@juni.io>

Co-authored-by: Nick Jüttner <nick@juni.io>

Skip address when TargetRef is nil

Increase AWS pagination size

Add the ability to configure k8s event rate limit

Co-authored-by: Raffaele Di Fazio <raffo@github.com>

Downgrade Azure provider "Failed to extract" log message to debug

When running the Azure provider at default log level, this messages
is 1/min and is the only messge in the log. Debug seems more
reasonable and matches what Azure Private provider.

Signed-off-by: Timtor Chen <to@timtor.dev>

feat: add gloo proxy source

Add Initial BlueCat Provider Support

rfc2136: Add cli flag for Kerberos realm and improve tutorial

updated ingress apiVersion

The new BlueCat provider uses the BlueCat API Gateway(REST API). Not
the legacy XML based BlueCat API.

https://github.com/bluecatlabs/gateway-workflows

Currently, the minimum delay between 2 kubernetes events handling is
hard-coded to 5s.

This may cause higher synchronization rates and higher DNS provider API
calls when handling an important number of kubernetes events at once.

Give the opportunity to configure this delay so service owners can
define the acceptable thresholds on their side

Approve crd v1

remove outdated provider list from FAQ, link to list in README