add Azure Pipelines Scaler doc

Signed-off-by: Troy <troydenorme@hotmail.com>

content/docs/2.3/scalers/azure-pipelines.md

@@ -0,0 +1,85 @@
++++
+title = "Azure Pipelines"
+layout = "scaler"
+availability = "v2.3+"
+maintainer = "Community"
+description = "Scale applications based on Azure Pipelines Queues."
+go_file = "azure_pipelines_scaler"
++++
+
+### Trigger Specification
+
+This specification describes the `azure-pipelines` trigger for Azure Pipelines Queue. It scales based on the queue length of Azure DevOps jobs in a given Agent Pool.
+
+```yaml
+triggers:
+  - type: azure-pipelines
+    metadata:
+      # Required: PoolId - Can be retreived by the REST API call https://dev.azure.com/{organizationName}/_apis/distributedtask/pools?poolname={agentPoolName}
+      poolId: "1"
+      # Optional: Azure DevOps organization URL, can use TriggerAuthentication as well
+      organizationUrlFromEnv: "AZP_URL"
+      # Optional: Azure DevOps Personal Access Token, can use TriggerAuthentication as well
+      personalAccessTokenFromEnv: "AZP_TOKEN"
+      # Optional: Target queue length
+      targetPipelinesQueueLength: "1" # Default 1
+    authenticationRef:
+     name: pipeline-trigger-auth
+```
+
+**Parameter list:**
+
+- `poolId` - Id of the queue.
+- `organizationUrlFromEnv` - Name of the environment variable your deployment uses to get the organizationUrl string.
+- `personalAccessTokenFromEnv` - Name of the environment variable your deployment uses to get the personalAccessToken string.
+- `targetPipelinesQueueLength` - Target value for queue length passed to the scaler. Example: if one pod can handle 10 jobs, set the queue length target to 10. If the actual number of jobs in the queue is 30, the scaler scales to 3 pods. (default: 1)
+
+### Authentication Parameters
+
+As an alternative to using environment variables, you can authenticate with Azure Devops using a Personal Access Token via `TriggerAuthentication` configuration.
+
+**Personal Access Token Authentication:**
+
+- `organizationUrl` - The Azure DevOps organization
+- `personalAccessToken` - The Azure DevOps Personal Access Token
+
+### Example
+
+```yaml
+apiVersion: v1
+kind: Secret
+type: Opaque
+metadata:
+  name: pipeline-auth
+data:
+  personalAccessToken: <encoded personalAccessToken>
+---
+apiVersion: keda.sh/v1alpha1
+kind: TriggerAuthentication
+metadata:
+  name: pipeline-trigger-auth
+  namespace: default
+spec:
+  secretTargetRef:
+    - parameter: personalAccessToken
+      name: pipeline-auth
+      key: personalAccessToken
+---
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name: azure-pipelines-scaledobject
+  namespace: default
+spec:
+  scaleTargetRef:
+    name: azdevops-deployment
+  minReplicaCount: 1
+  maxReplicaCount: 5 
+  triggers:
+  - type: azure-pipelines
+    metadata:
+      poolId: "1"
+      organizationUrlFromEnv: "AZP_URL"
+    authenticationRef:
+     name: pipeline-trigger-auth
+```