Add logging configuration example to the Configure inputs page (#489)

* Update standalone input settings docs to match elastic-agent.yml

* fixup

* Move simplfied input config to input page

* Re-add separate logging page

* Add input types tables

* Add input types tables; address comments

* touchup

* Remove list of agent inputs; I'll merge them as a separate PR

* Rebuild preview page

* Re-add inputs list link

* Rebuild

(cherry picked from commit 0c56b67)

docs/en/ingest-management/elastic-agent/configuration/inputs/input-configuration.asciidoc

@@ -7,38 +7,70 @@
 
 The `inputs` section of the `elastic-agent.yml` file specifies how {agent} locates and processes input data.
 
-By default {agent} collects system metrics, such as CPU, memory, network, and file system metrics, and sends them to the default output. For example, to define the datastream for `cpu` metrics, this is the configuration:
+* <<elastic-agent-input-configuration-sample-metrics>>
+* <<elastic-agent-input-configuration-sample-logs>>
+
+[discrete]
+[[elastic-agent-input-configuration-sample-metrics]]
+== Sample metrics input configuration
+
+By default {agent} collects system metrics, such as CPU, memory, network, and file system metrics, and sends them to the default output. For example, to define datastreams for `cpu`, `memory`, `network` and `filesystem` metrics, this is the configuration:
 
 ["source","yaml"]
 -----------------------------------------------------------------------
-- id: unique-system-metrics-id <1>
-  type: system/metrics <2>
-  use_output: default <3>
-  meta:
-    package: <4>
-      name: system
-      version: 0.10.9
-  data_stream:
-    namespace: default <5>
+- type: system/metrics <1>
+  id: unique-system-metrics-id <2>
+  data_stream.namespace: default <3>
+  use_output: default <4>
   streams:
-    - data_stream:
-        dataset: system.cpu <6>
-        type: metrics <7>
-      metricsets: <8>
-        - cpu
-      period: 10s
-      cpu.metrics:
-        - percentages
-        - normalized_percentages
+    - metricsets: <5>
+      - cpu
+      data_stream.dataset: system.cpu <6>
+    - metricsets:
+      - memory
+      data_stream.dataset: system.memory
+    - metricsets:
+      - network
+      data_stream.dataset: system.network
+    - metricsets:
+      - filesystem
+      data_stream.dataset: system.filesystem
 -----------------------------------------------------------------------
 
-<1> A unique ID for the input.
-<2> The name of the input. Refer to <<elastic-agent-inputs-list>> for the list of what's available.
-<3> The name of the `output` to use. If not specified, `default` will be used.
-<4> Package specification.
-<5> A user-defined namespace.
-<6> A user-defined dataset. It can contain anything that makes sense to signify the source of the data.
-<7> The type of the data stream.
-<8> Enabled module metricsets.
+<1> The name of the input. Refer to <<elastic-agent-inputs-list>> for the list of what's available.
+<2> A unique ID for the input.
+<3> A user-defined namespace.
+<4> The name of the `output` to use. If not specified, `default` will be used.
+<5> The set of enabled module metricsets.
 +
-In the {metricbeat-ref}/metricbeat-module-system.html[System module] there are several options. The `cpu` is just one of them. Its fields can be configured.
+Refer to the {metricbeat} {metricbeat-ref}/metricbeat-module-system.html[System module] for a list of available options. The metricset fields can be configured.
+<6> A user-defined dataset. It can contain anything that makes sense to signify the source of the data.
+
+[discrete]
+[[elastic-agent-input-configuration-sample-logs]]
+== Sample log files input configuration
+
+To enable {agent} to collect log files, you can use a configuration like the following.
+
+["source","yaml"]
+-----------------------------------------------------------------------
+- type: filestream <1>
+  id: your-input-id <2>
+  streams:
+    - id: your-filestream-stream-id <3>
+      data_stream: <4>
+        dataset: generic
+      paths:
+        - /var/log/*.log
+-----------------------------------------------------------------------
+
+<1> The name of the input. Refer to <<elastic-agent-inputs-list>> for the list of what's available.
+<2> A unique ID for the input.
+<3> A unique ID for the data stream to track the state of the ingested files.
+<4> The streams block is required only if multiple streams are used on the same input. Refer to the {filebeat} {filebeat-ref}/filebeat-input-filestream.html[filestream] documentation for a list of available options. Also, specifically for the `filestream` input type, refer to the <<elastic-agent-simplified-input-configuration,simplified log ingestion>> for an example of ingesting a set of logs specified as an array.
+
+The input in this example harvests all files in the path `/var/log/*.log`, that is, all logs in the directory `/var/log/` that end with `.log`. All patterns supported by https://golang.org/pkg/path/filepath/#Glob[Go Glob] are also supported here.
+
+To fetch all files from a predefined level of subdirectories, use this pattern:
+`/var/log/*/*.log`. This fetches all `.log` files from the subfolders of `/var/log`. It does not fetch log files from the `/var/log` folder itself.
+Currently it is not possible to recursively fetch all files in all subdirectories of a directory.