Added tutorial for configuring DC2DC of Kubernetes

docs/Manual/Tutorials/Kubernetes/DC2DC.md

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+# Start ArangoDB Cluster to Cluster Synchronization on Kubernetes
+
+This tutorial guides you through the steps needed to configure
+an ArangoDB datacenter to datacenter replication between two ArangoDB
+clusters running in Kubernetes.
+
+## Requirements
+
+1. This tutorial assumes that you 2 ArangoDB clusters running in 2 different Kubernetes clusters.
+1. Both Kubernetes clusters are equiped with support for `Services` of type `LoadBalancer`.
+1. You can create (global) DNS names for configured `Services` with low propagation times. E.g. use Cloudflare.
+1. You have 4 DNS names available:
+   - One for the database in the source ArangoDB cluster. E.g. `src-db.mycompany.com`
+   - One for the ArangoDB syncmasters in the source ArangoDB cluster. E.g. `src-sync.mycompany.com`
+   - One for the database in the destination ArangoDB cluster. E.g. `dst-db.mycompany.com`
+   - One for the ArangoDB syncmasters in the destination ArangoDB cluster. E.g. `dst-sync.mycompany.com`
+
+## Step 1: Enable Datacenter Replication Support on source ArangoDB cluster
+
+Set your current Kubernetes context to the Kubernetes source cluster.
+
+Edit the `ArangoDeployment` of the source ArangoDB clusters.
+
+Set:
+
+- `spec.tls.altNames` to `["src-db.mycompany.com"]` (can include more names / IP addresses)
+- `spec.sync.enabled` to `true`
+- `spec.sync.externalAccess.masterEndpoint` to `["https://src-sync.mycompany.com:8629"]`
+- `spec.sync.externalAccess.accessPackageSecretNames` to `["src-accessPackage"]`
+
+## Step 2: Extract access-package from source ArangoDB cluster
+
+Run:
+
+```bash
+kubectl get secret src-accessPackage --template='{{index .data "accessPackage.yaml"}}' | \
+  base64 -D > accessPackage.yaml
+```
+
+## Step 3: Configure source DNS names
+
+Run:
+
+```bash
+kubectl get service
+```
+
+Find the IP address contained in the `LoadBalancer` column for the following `Services`:
+
+- `<deployment-name>-ea` Use this IP address for the `src-db.mycompany.com` DNS name.
+- `<deployment-name>-sync` Use this IP address for the `src-sync.mycompany.com` DNS name.
+
+The process for configuring DNS names is specific to each DNS provider.
+
+## Step 4: Enable Datacenter Replication Support on destination ArangoDB cluster
+
+Set your current Kubernetes context to the Kubernetes destination cluster.
+
+Edit the `ArangoDeployment` of the source ArangoDB clusters.
+
+Set:
+
+- `spec.tls.altNames` to `["dst-db.mycompany.com"]` (can include more names / IP addresses)
+- `spec.sync.enabled` to `true`
+- `spec.sync.externalAccess.masterEndpoint` to `["https://dst-sync.mycompany.com:8629"]`
+
+## Step 5: Import access package in destination cluster
+
+Run:
+
+```bash
+kubectl apply -f accessPackage.yaml
+```
+
+Note: This imports two `Secrets`, containing TLS information about the source cluster,
+into the destination cluster
+
+## Step 6: Configure destination DNS names
+
+Run:
+
+```bash
+kubectl get service
+```
+
+Find the IP address contained in the `LoadBalancer` column for the following `Services`:
+
+- `<deployment-name>-ea` Use this IP address for the `dst-db.mycompany.com` DNS name.
+- `<deployment-name>-sync` Use this IP address for the `dst-sync.mycompany.com` DNS name.
+
+The process for configuring DNS names is specific to each DNS provider.
+
+## Step 7: Create an `ArangoDeploymentReplication` resource
+
+Create a yaml file (e.g. called `src-to-dst-repl.yaml`) with the following content:
+
+```yaml
+apiVersion: "replication.database.arangodb.com/v1alpha"
+kind: "ArangoDeploymentReplication"
+metadata:
+  name: "replication-src-to-dst"
+spec:
+  source:
+    masterEndpoint: ["https://src-sync.mycompany.com:8629"]
+    auth:
+      keyfileSecretName: src-accessPackage-auth
+    tls:
+      caSecretName: src-accessPackage-ca
+  destination:
+    deploymentName: <dst-deployment-name>
+```
+
+## Step 8: Wait for DNS names to propagate
+
+Wait until the DNS names configured in step 3 and 6 resolve to their configured
+IP addresses.
+
+Depending on your DNS provides this can take a few minutes up to 24 hours.
+
+## Step 9: Activate replication
+
+Run:
+
+```bash
+kubectl apply -f src-to-dst-repl.yaml
+```
+
+Replication from the source cluster to the destination cluster will now be configured.
+
+Check the status of the replication by inspecting the status of the `ArangoDeploymentReplication` resource using:
+
+```bash
+kubectl describe ArangoDeploymentReplication replication-src-to-dst
+```
+
+As soon as the replication is configured, the `Add collection` button in the `Collections`
+page of the web UI (of the destination cluster) will be grayed out.