Adds alias action sample template to ISM policy page (#2269)

* Adds alias action sample template to ISM policy page

Signed-off-by: ariamarble <armarble@amazon.com>

* added copy buttons

Signed-off-by: ariamarble <armarble@amazon.com>

* Changes formatting for copy buttons

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

* made tech review changes

Signed-off-by: ariamarble <armarble@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* Update _im-plugin/ism/policies.md

Co-authored-by: Nate Bower <nbower@amazon.com>

* editorial

Signed-off-by: ariamarble <armarble@amazon.com>

Signed-off-by: ariamarble <armarble@amazon.com>
Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>
Co-authored-by: Fanit Kolchina <kolchfa@amazon.com>
Co-authored-by: Nate Bower <nbower@amazon.com>

_im-plugin/ism/policies.md

@@ -789,6 +789,128 @@ If you want to skip rollovers for an index, set `index.plugins.index_state_manag
    GET _plugins/_ism/explain/log-000001?pretty
    ```
 
+## Example policy with ISM templates for the alias action
+
+The following example policy is for an alias action use case.
+
+In the following example, the first job will trigger the rollover action, and a new index will be created. Next, another document is added to the two indexes. The new job will then cause the second index to point to the log alias, and the older index will be removed due to the alias action.
+
+First, create an ISM policy:
+
+```json
+PUT /_plugins/_ism/policies/rollover_policy?pretty
+{
+  "policy": {
+    "description": "Example rollover policy.",
+    "default_state": "rollover",
+    "states": [
+      {
+        "name": "rollover",
+        "actions": [
+          {
+            "rollover": {
+              "min_doc_count": 1
+            }
+          }
+        ],
+        "transitions": [{
+            "state_name": "alias",
+            "conditions": {
+              "min_doc_count": "2"
+            }
+          }]
+      },
+      {
+        "name": "alias",
+        "actions": [
+          {
+            "alias": {
+              "actions": [
+                {
+                  "remove": {
+                      "alias": "log"
+                  }
+                }
+              ]
+            }
+          }
+        ]
+      }
+    ],
+    "ism_template": {
+      "index_patterns": ["log*"],
+      "priority": 100
+    }
+  }
+}
+```
+
+Next, create an index template on which to enable the policy:
+
+```json
+PUT /_index_template/ism_rollover?
+{
+  "index_patterns": ["log*"],
+  "template": {
+   "settings": {
+    "plugins.index_state_management.rollover_alias": "log"
+   }
+ }
+}
+```
+{% include copy-curl.html %}
+
+Next, change the cluster settings to trigger jobs every minute:
+
+```json
+PUT /_cluster/settings?pretty=true
+{
+  "persistent" : {
+    "plugins.index_state_management.job_interval" : 1
+  }
+}
+```
+{% include copy-curl.html %}
+
+Next, create a new index:
+
+```json
+PUT /log-000001
+{
+  "aliases": {
+    "log": {
+      "is_write_index": true
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+Finally, add a document to the index to trigger the job:
+
+```json
+POST /log-000001/_doc
+{
+  "message": "dummy"
+}
+```
+{% include copy-curl.html %}
+
+You can verify these steps using the Alias and Index API:
+
+```json
+GET /_cat/indices?pretty
+```
+{% include copy-curl.html %}
+
+```json
+GET /_cat/aliases?pretty
+```
+{% include copy-curl.html %}
+
+Note: The `index` and `remove_index` parameters are not allowed with alias action policies. Only the `add` and `remove` alias action parameters are allowed.
+{: .warning }
+
 ## Example policy
 
 The following example policy implements a `hot`, `warm`, and `delete` workflow. You can use this policy as a template to prioritize resources to your indexes based on their levels of activity.