Add 'bluecat' as possible option to the provider flag

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

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>

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.

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remove outdated provider list from FAQ, link to list in README

From measurements, AWS by default has pagination of 100 items per
page when listing hosted zone resources.

This increases the number of requests required to list all our zones,
and pushes a hard constraint on the rate limits.

From the experiments, it seems that on the server-side, there is a hard
limit of 300 elements per page, as per AWS documentation:
https://docs.aws.amazon.com/Route53/latest/APIReference/API_ListResourceRecordSets.html

> ListResourceRecordSets returns up to 300 resource record sets at a time in ASCII order,
> beginning at a position specified by the name and type elements

Hence raising the page size from 100 to 300 items would decrease by 3
the number of requests posted to Route53

We even set a higher limit so we can benefit from a lower number of
requests if ever AWS increases the hard limit of 300.

All CRDs under k8s.io and kubernetes.io API groups should go through API
approval.
Signed-off-by: Dinar Valeev <dinar.valeev@absa.africa>

Switch to controller-gen for CRD generation and update CRD to apiextentions v1

external-dns configuration update

Bump alpine base image to 3.13

updated to latest Istio 1.7 libs

v1 is available since kubernetes 1.16, since then v1beta1 is deprecated
and will be dropped in kubernetes 1.22
Signed-off-by: Dinar Valeev <dinar.valeev@absa.africa>

Signed-off-by: Dinar Valeev <dinar.valeev@absa.africa>