PMM-9146 provide an endpoint to modify custom labels

Author: ademidoff

documentation/docs/admin/roles/access-control/labels.md

@@ -8,7 +8,7 @@ With label-based access control, you can associate multiple labels with a role,
 
 ## Standard vs custom labels
 
-PMM supports standard as well as custom labels. When the user adds a service to monitoring, PMM automatically assigns some standard labels. Thease labels are mostly based on the type of service being added to monitoring, such as `service_type`, `agent_type`, `node_name`, etc. Some other labels are auto-generated by PMM, for example, `service_id`, `node_id`, etc. Normally, the user can override standard labels when an object –– Node, Service, or Agent –– is created. There is also a possibility to define custom labels when adding objects. Custom labels, however, are assigned and updated only by the user.
+PMM supports standard as well as custom labels. When the user adds a service to monitoring, PMM automatically assigns some standard labels. Thease labels are mostly based on the type of service being added to monitoring, such as `service_type`, `agent_type`, `node_name`, etc. Some other labels are auto-generated by PMM, for example, `service_id`, `node_id`, etc. Normally, the user can override standard labels when an object — Node, Service, or Agent — is created. There is also a possibility to define custom labels when adding objects. Custom labels, however, are assigned and updated only by the user.
 
 It's important to note that standard labels are not always available for all objects. For example, the `service_type` label is only available for services, while the `agent_type` label is only available for agents.
 
@@ -17,20 +17,22 @@ Both standard and custom labels are persisted during the metrics collection proc
 **Examples**
 
 | **Label Type**| **Object**| **Label name ** | **Example** |                                                                                                
-|---------------|-----------|-----------------|-------------|
-| **Standard**  | Node      | node_id         | 123 |                                          
-| **Standard**  | Service   | service_type    | mysql, mongodb, postgresql etc. |
+|---------------|-----------|-----------------|--------------------------------------|
+| **Standard**  | Node      | node_id         | 5bdfb1b4-c6c4-4086-83a2-e8daa0b84d4b |                                          
+| **Standard**  | Service   | service_type    | mysql, mongodb, postgresql etc.      |
 | **Custom**    | Node, Service, Agent | Any string matching the regular expression: <br /> [a-zA-Z_][a-zA-Z0-9_]*. <br /> Also, it cannot start with two underscores.| owner="joe"<br/> _rack="12345"|
 
 ## Assigning labels
 
-You can assign custom or standard labels while adding a service to monitoring in PMM.
+You can assign standard or custom labels while adding a service to monitoring in PMM.
 
 ## Modifying labels
 
 Currently, PMM does not support modifying standard labels. To modify a standard label, you first need to remove the service and re-add it with a new set of standard labels.
 
-However, you can modify custom labels. 
+However, you can modify custom labels of a service via an [API endpoint](https://percona-pmm.readme.io/reference/changeservice).
+
+```bash
 
 ### Using PMM UI