Added the Host cleanup API documentation

Signed-off-by: Ihor Aleksandrychiev <ihor.aleksandrychiev@northern.tech>

Author: aleksandrychev

content/api/enterprise-api-ref/host-cleanup.markdown

@@ -0,0 +1,82 @@
+---
+layout: default
+title: Host cleanup API
+---
+
+The Hosts cleanup API removes hosts from the hub based on multiple
+criteria configured in the hub settings.
+
+## Run hosts cleanup
+
+Runs all enabled cleanup stages sequentially and returns statistics for each stage.
+
+**URI:** https://hub.cfengine.com/api/host-cleanup
+
+**Method:** POST
+
+**Prerequisites:**
+
+Hosts cleanup is configured through the [hub settings][Hosts cleanup API#Settings]
+
+This endpoint is not available on a [federated reporting][Federated reporting] superhub.
+
+**Example request (curl):**
+
+```console
+curl --user <username>:<password> \
+  -X POST \
+  https://hub.cfengine.com/api/host-cleanup
+```
+
+**Example response:**
+
+```
+HTTP 200 OK
+{
+  "deletedHostsCleanup": {
+    "found": 0,
+    "permanentlyDeleted": 0,
+    "failed": 0
+  },
+  "duplicateHostnameHostsCleanup": {
+    "found": 0,
+    "softDeleted": 0,
+    "permanentlyDeleted": 0,
+    "failed": 0
+  },
+  "duplicateIpHostsCleanup": {
+    "found": 1,
+    "softDeleted": 1,
+    "permanentlyDeleted": 0,
+    "failed": 0
+  },
+  "groupHostsCleanup": {
+    "found": 0,
+    "softDeleted": 0,
+    "permanentlyDeleted": 0,
+    "failed": 0
+  },
+  "InactiveHostsCleanup": {
+    "found": 0,
+    "softDeleted": 0,
+    "permanentlyDeleted": 0,
+    "failed": 0
+  }
+}
+```
+
+Each stage runs independently. If a stage fails, an `error` field with the error message
+is returned in place of the counters and the remaining stages still run. A maximum of
+1000 hosts is processed per stage per call.
+
+**Responses:**
+
+| HTTP response code | Description                              |
+| ------------------ | ---------------------------------------- |
+| 200 OK             | Cleanup ran; the body contains per-stage statistics. |
+| 403 Forbidden      | Endpoint called on a federated reporting superhub. |
+
+## Settings
+
+The behavior of each stage is controlled by the settings keys, managed
+through the [Status and settings REST API][Status and settings REST API#Update settings].