Add APIClient intro page (#289)

docs/clearml_sdk/apiclient_sdk.md

@@ -0,0 +1,32 @@
+---
+title: APIClient
+---
+
+The `APIClient` class provides a Pythonic interface to access ClearML's backend REST API. It is a convenient low-level access tool. 
+Through an `APIClient` instance, you can access ClearML’s REST API services:
+* [authentication](../references/api/login.md) - Authentication management, authorization and administration for the entire system
+* [debug](../references/api/debug.md) - Debugging utilities
+* [projects](../references/api/projects.md) - Support for defining Projects containing tasks, models, datasets, and/or pipelines 
+* [queues](../references/api/queues.md) - [Queue](../fundamentals/agents_and_queues.md) management API
+* [workers](../references/api/workers.md) - API for worker machines to report status and retrieve tasks for execution.
+* [events](../references/api/events.md) - Event (e.g. metrics, debug samples) reporting and retrieval API
+* [models](../references/api/models.md) - Model management API
+* [tasks](../references/api/tasks.md) - [Task](../fundamentals/task.md) Management API
+
+## Using APIClient
+
+`APIClient` makes the ClearML Server’s REST API endpoints available as Python methods. 
+
+To use `APIClient`, create an instance of it then call the method corresponding to the desired REST API endpoints, with 
+its respective parameters as described in the [REST API reference page](../references/api/index.md). 
+
+For example, the [`POST/ projects.get_all`](../references/api/projects.md#post-projectsget_all) call returns all projects 
+in your workspace. The following code uses APIClient to retrieve a list of all projects whose name starts with "example."
+
+```python
+from clearml.backend_api.session.client import APIClient
+# Create an instance of APIClient
+client = APIClient()
+project_list = client.projects.get_all(name="example*")
+print(project_list)
+```

docs/clearml_sdk/clearml_sdk.md

@@ -84,6 +84,11 @@ including local folders, S3, Google Cloud Storage, Azure Storage, and http(s).
 
 See the [StorageManager SDK reference page](../references/sdk/storage.md).
 
+### APIClient
+The `APIClient` class provides a Pythonic interface to access ClearML's backend REST API.
+
+See an [overview](apiclient_sdk.md) for APIClient usage. 
+
 ### ClearmlJob 
 Use the ClearmlJob to create and manage jobs based on existing tasks. The class supports changing a job's parameters, 
 configurations, and other execution details. 

sidebars.js

@@ -15,7 +15,7 @@ module.exports = {
         }, 'getting_started/architecture']},
         {'ClearML Fundamentals': ['fundamentals/projects', 'fundamentals/task', 'fundamentals/hyperparameters', 'fundamentals/artifacts', 'fundamentals/logger', 'fundamentals/agents_and_queues',
             'fundamentals/hpo']},
-        {'ClearML SDK': ['clearml_sdk/clearml_sdk', 'clearml_sdk/task_sdk', 'clearml_sdk/model_sdk']},
+        {'ClearML SDK': ['clearml_sdk/clearml_sdk', 'clearml_sdk/task_sdk', 'clearml_sdk/model_sdk', 'clearml_sdk/apiclient_sdk']},
         'clearml_agent',
         {'ClearML Pipelines':['pipelines/pipelines',
                 {"Building Pipelines":