docs: configuring custom headers in the dataproxy (#17367)

closes #17348

docs/sources/administration/provisioning.md

@@ -179,6 +179,24 @@ Secure json data is a map of settings that will be encrypted with [secret key](/
 | accessKey | string | Cloudwatch | Access key for connecting to Cloudwatch |
 | secretKey | string | Cloudwatch | Secret key for connecting to Cloudwatch |
 
+#### Custom HTTP headers for datasources
+Datasources managed by Grafanas provisioning can be configured to add HTTP headers to all requests
+going to that datasource. The header name is configured in the `jsonData` field and the header value should be
+configured in `secureJsonData`.
+
+```yaml
+apiVersion: 1
+
+datasources:
+- name: Graphite
+  jsonData:
+    httpHeaderName1: "HeaderName"
+    httpHeaderName2: "Authorization"
+  secureJsonData:
+    httpHeaderValue1: "HeaderValue"
+    httpHeaderValue2: "Bearer XXXXXXXXX"
+```
+
 ### Dashboards
 
 It's possible to manage dashboards in Grafana by adding one or more yaml config files in the [`provisioning/dashboards`](/installation/configuration/#provisioning) directory. Each config file can contain a list of `dashboards providers` that will load dashboards into Grafana from the local filesystem.