Move Pulsar IO as a top-category section at the sidebar (apache#2050)

*Motivation*

Pulsar I/O is too deep in the documentation. It is hard for people to realize the connectors.

*Changes*

Move Pulsar I/O documentation to a top-category section.

Also renaming "pulsar administration" to "Administration"

site/_data/sidebar.yaml

@@ -49,6 +49,15 @@ groups:
   - title: Metrics for Pulsar Functions
     endpoint: metrics
 
+- title: Pulsar IO
+  dir: io
+  new: true
+  docs:
+  - title: Pulsar IO overview
+    endpoint: overview
+  - title: Getting started with Pulsar IO
+    endpoint: quickstart
+
 - title: Deployment
   dir: deployment
   docs:
@@ -69,7 +78,7 @@ groups:
   - title: Monitoring
     endpoint: Monitoring
 
-- title: Pulsar administration
+- title: Administration
   dir: admin
   docs:
   - title: ZooKeeper and BookKeeper
@@ -136,8 +145,6 @@ groups:
 - title: Cookbooks
   dir: cookbooks
   docs:
-  - title: Pulsar IO
-    endpoint: pulsar-io
   - title: Tiered Storage
     endpoint: tiered-storage
   - title: Topic compaction

site/docs/latest/getting-started/ConceptsAndArchitecture.md

@@ -585,34 +585,6 @@ Pulsar currently supports S3 as a long term store. Offloading to S3 triggered vi
 
 {% include admonition.html type="info" content="For a guide for setting up tiered storage, see the [Tiered storage cookbook](../../cookbooks/tiered-storage)." %}
 
-## Pulsar IO
-
-Messaging systems are most powerful when you can easily use them in conjunction with external systems like databases and other messaging systems. **Pulsar IO** is a feature of Pulsar that enables you to easily create, deploy, and manage Pulsar **connectors** that interact with external systems, such as [Apache Cassandra](https://cassandra.apache.org), [Aerospike](https://www.aerospike.com), and many others.
-
-{% include admonition.html type="info" title="Pulsar IO and Pulsar Functions"
-   content="Under the hood, Pulsar IO connectors are specialized [Pulsar Functions](#pulsar-functions) purpose-built to interface with external systems. The [administrative interface](../../cookbooks/pulsar-io) for Pulsar IO is, in fact, quite similar to that of Pulsar Functions." %}
-
-### Sources and sinks
-
-Pulsar IO connectors come in two types:
-
-* **Sources** feed data *into* Pulsar from other systems. Common sources include other messaging systems and "firehose"-style data pipeline APIs.
-* **Sinks** are fed data *from* Pulsar. Common sinks include other messaging systems and SQL and NoSQL databases.
-
-This diagram illustrates the relationship between sources, sinks, and Pulsar:
-
-{% include figure.html src="/img/pulsar-io.png" alt="Pulsar IO diagram" caption="Pulsar IO connectors (sources and sinks)" width="80" %}
-
-### Working with connectors
-
-Pulsar IO connectors can be managed via the [`pulsar-admin`](../../reference/CliTools#pulsar-admin) CLI tool, in particular the [`source`](../../reference/CliTools#pulsar-admin-source) and [`sink`](../../reference/CliTools#pulsar-admin-sink) commands.
-
-{% include admonition.html type="info" content="For a guide to managing connectors in your Pulsar installation, see the [Pulsar IO cookbook](../../cookbooks/pulsar-io#managing-connectors)." %}
-
-The following connectors are currently available for Pulsar:
-
-{% include connectors.html %}
-
 ## Schema registry
 
 Type safety is extremely important in any application built around a message bus like Pulsar. {% popover Producers %} and {% popover consumers %} need some kind of mechanism for coordinating types at the {% popover topic %} level lest a wide variety of potential problems arise (for example serialization and deserialization issues). Applications typically adopt one of two basic approaches to type safety in messaging:

site/docs/latest/io/overview.md

@@ -0,0 +1,51 @@
+---
+title: Pulsar IO overview
+lead: Connecting the world using Pulsar Functions
+---
+
+<!--
+
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+
+-->
+
+Messaging systems are most powerful when you can easily use them in conjunction with external systems like databases and other messaging systems. **Pulsar IO** is a feature of Pulsar that enables you to easily create, deploy, and manage Pulsar **connectors** that interact with external systems, such as [Apache Cassandra](https://cassandra.apache.org), [Aerospike](https://www.aerospike.com), and many others.
+
+{% include admonition.html type="info" title="Pulsar IO and Pulsar Functions"
+   content="Under the hood, Pulsar IO connectors are specialized [Pulsar Functions](../../functions/overview) purpose-built to interface with external systems. The [administrative interface](../quickstart) for Pulsar IO is, in fact, quite similar to that of Pulsar Functions." %}
+
+## Sources and sinks
+
+Pulsar IO connectors come in two types:
+
+* **Sources** feed data *into* Pulsar from other systems. Common sources include other messaging systems and "firehose"-style data pipeline APIs.
+* **Sinks** are fed data *from* Pulsar. Common sinks include other messaging systems and SQL and NoSQL databases.
+
+This diagram illustrates the relationship between sources, sinks, and Pulsar:
+
+{% include figure.html src="/img/pulsar-io.png" alt="Pulsar IO diagram" caption="Pulsar IO connectors (sources and sinks)" width="80" %}
+
+## Working with connectors
+
+Pulsar IO connectors can be managed via the [`pulsar-admin`](../../reference/CliTools#pulsar-admin) CLI tool, in particular the [`source`](../../reference/CliTools#pulsar-admin-source) and [`sink`](../../reference/CliTools#pulsar-admin-sink) commands.
+
+{% include admonition.html type="info" content="For a guide to managing connectors in your Pulsar installation, see the [Getting started with Pulsar IO](../quickstart)." %}
+
+The following connectors are currently available for Pulsar:
+
+{% include connectors.html %}

site/docs/latest/cookbooks/pulsar-io.md → site/docs/latest/io/quickstart.md

@@ -1,5 +1,6 @@
 ---
-title: The Pulsar IO cookbook
+title: Getting started with Pulsar IO
+lead: Connecting your systems with Pulsar using Pulsar IO
 ---
 
 <!--
@@ -80,3 +81,4 @@ Instead of submitting a sink to run on an existing Pulsar cluster, you alternati
 At the moment, the following connectors are available for Pulsar:
 
 {% include connectors.html %}
+