API design: API endpoint for updating a host's manual labels (#16979)

API design for: 
- #16767

---------

Co-authored-by: Rachael Shaw <r@rachael.wtf>

docs/REST API/rest-api.md

@@ -1865,6 +1865,8 @@ None.
 - [Wipe host](#wipe-host)
 - [Get host's past activity](#get-hosts-past-activity)
 - [Get host's upcoming activity](#get-hosts-upcoming-activity)
+- [Add labels to host](#add-labels-to-host)
+- [Remove labels from host](#remove-labels-from-host)
 - [Live query one host (ad-hoc)](#live-query-one-host-ad-hoc)
 - [Live query host by identifier (ad-hoc)](#live-query-host-by-identifier-ad-hoc)
 
@@ -4037,6 +4039,64 @@ To wipe a macOS or Windows host, the host must have MDM turned on. To lock a Lin
 }
 ```
 
+### Add labels to host
+
+Adds manual labels to a host. 
+
+`POST /api/v1/fleet/hosts/:id/labels`
+
+#### Parameters
+
+| Name | Type    | In   | Description                  |
+| ---- | ------- | ---- | ---------------------------- |
+| labels   | list | body | The list of label names to add to the host. |
+
+
+#### Example
+
+`POST /api/v1/fleet/hosts/12/labels`
+
+##### Request body
+
+```json
+{
+  "labels": ["label1", "label2"]
+}
+```
+
+##### Default response
+
+`Status: 200`
+
+### Remove labels from host
+
+Removes manual labels from a host.
+
+`DELETE /api/v1/fleet/hosts/:id/labels`
+
+#### Parameters
+
+| Name | Type    | In   | Description                  |
+| ---- | ------- | ---- | ---------------------------- |
+| labels   | list | body | The list of label names to delete from the host. |
+
+
+#### Example
+
+`DELETE /api/v1/fleet/hosts/12/labels`
+
+##### Request body
+
+```json
+{
+  "labels": ["label3", "label4"]
+}
+```
+
+##### Default response
+
+`Status: 200`
+
 ### Live query one host (ad-hoc)
 
 Runs an ad-hoc live query against the specified host and responds with the results.