Add docs about EEM and new Services inventory (#4062)

* Add docs about EEM and entity-centric services inventory

---------

Co-authored-by: Mike Birnstiehl <[email protected]>

docs/en/serverless/apm/apm-ui-services.mdx

@@ -21,6 +21,10 @@ In addition to health status, active alerts for each service are prominently dis
 
 ![Example view of services table the Applications UI](images/services/apm-services-overview.png)
 
+<DocCallOut title="Tip">
+   Want to monitor service logs without instrumenting all your services? Learn about our <DocLink slug="/serverless/observability/new-experience-services">new services experience.</DocLink>
+</DocCallOut>
+
 ## Service groups
 
 import Roles from '../partials/roles.mdx'

docs/en/serverless/apm/new-experience-services.mdx

@@ -0,0 +1,52 @@
+---
+slug: /serverless/observability/new-experience-services
+title: New services experience
+description: Try out our new Services inventory, which enables you to monitor service logs without instrumenting all your services.
+tags: [ 'serverless', 'observability', 'overview' ]
+---
+
+<DocBadge template="technical preview" />
+
+With this technical preview,
+Elastic expands the **Services** inventory to include services found in logs.
+This means you can monitor the services you care about even if you only have logs
+and aren't ready to instrument your services.
+
+The new **Services** inventory shows services instrumented with APM or OpenTelemetry,
+plus any services declared using `service.name` in your logs:
+
+<DocImage url="../images/entity-centric-services-inventory.png" alt="Services inventory that shows APM data and log data"/>
+
+For instrumented services that also have custom logs, the APM and log data are displayed in the same view.
+For services that only have log data,
+the log data is displayed, and you have the option of adding APM later.
+
+<DocCallOut title="Note">
+   The new **Services** inventory requires the Elastic Entity Model (EEM). To learn more, refer to <DocLink slug="/serverless/observability/elastic-entity-model" />.
+</DocCallOut>
+
+## Turn on the new experience
+
+The new services experience is turned off by default. To turn it on:
+
+1. In your ((observability)) project, go to **Applications** → **Services**.
+1. Click **Try out Elastic's new experience!**
+
+If you have **Admin** privileges, the EEM will be turned on automatically.
+Otherwise, you need to ask someone with **Admin** privileges to turn on this feature under **Stack Management**.
+
+To turn off the new experience, click **Restore classic view**.
+You can switch back and forth between the new and classic views whenever you want.
+
+<DocCallOut title="Does turning on the new experience affect other users?">
+   No. The settings are applied at the browser level,
+   which means that other users need to turn on the new experience if they want to use it.
+</DocCallOut>
+
+## Add services to the inventory
+
+To add services to the inventory, use one of the following approaches:
+
+* Instrument your services with APM or OpenTelemetry.
+To learn how, refer to <DocLink slug="/serverless/observability/apm-send-data-to-elastic" />.
+* Declare `service.name` in your logs. To learn how, refer to <DocLink slug="/serverless/observability/add-logs-service-name" />.

docs/en/serverless/elastic-entity-model.mdx

@@ -0,0 +1,40 @@
+---
+slug: /serverless/observability/elastic-entity-model
+title: Elastic Entity Model
+description: Learn about the model that empowers entity-centric Elastic solution features and workflows.
+tags: [ 'serverless', 'observability', 'overview' ]
+---
+
+import Roles from './partials/roles.mdx'
+
+<p><DocBadge template="technical preview" /></p>
+
+The Elastic Entity Model consists of:
+
+- a data model and related entity indices
+- an Entity Discovery Framework, which consists of [transforms](((ref))/transforms.html) and [Ingest pipelines](((ref))/ingest.html) that read from signal indices and write data to entity indices
+- a set of management APIs that empower entity-centric Elastic solution features and workflows
+
+In the context of Elastic Observability,
+an _entity_ is an object of interest that can be associated with produced telemetry and identified as unique.
+Note that this definition is intentionally closely aligned to the work of the [OpenTelemetry Entities SIG](https://github.com/open-telemetry/oteps/blob/main/text/entities/0256-entities-data-model.md#data-model).
+Examples of entities include (but are not limited to) services, hosts, and containers.
+
+The concept of an entity is important as a means to unify observability signals based on the underlying entity that the signals describe.
+
+## Enable or disable the Elastic Entity Model
+
+<Roles role="Admin" goal="enable or disable the Elastic Entity Model" />
+
+
+During Technical Preview,
+the Elastic Entity Model is enabled when you turn on the entity-centric service inventory described in <DocLink slug="/serverless/observability/new-experience-services" />.
+
+**To disable the Elastic Entity Model:**
+
+- From the Dev Console, run the command: `DELETE kbn:/internal/entities/managed/enablement`
+
+<DocCallOut title="Notes">
+    - The Elastic Entity Model currently supports the <DocLink slug="/serverless/observability/new-experience-services">new service inventory experience</DocLink> limited to service-based entities (as identified by `service.name`) located in data identified by `logs-*` and `trace-*` index patterns
+    - During Technical Preview, Entity Discovery Framework components are not enabled by default
+</DocCallOut>

docs/en/serverless/serverless-observability.docnav.json

@@ -210,6 +210,11 @@
                   "slug": "/serverless/observability/apm-services",
                   "classic-sources": [
                     "enKibanaServices"
+                  ],
+                  "items": [
+                    {
+                      "slug": "/serverless/observability/new-experience-services"
+                    }
                   ]
                 },
                 {
@@ -637,6 +642,9 @@
       "slug": "/serverless/observability/ai-assistant",
       "classic-sources": [ "enObservabilityObsAiAssistant" ]
     },
+    {
+      "slug": "/serverless/observability/elastic-entity-model"
+    },
     {
       "slug": "/serverless/observability/observability-technical-preview-limitations"
     }