docs: add public documentation for declarative oauth (airbytehq#52041)

Co-authored-by: Oleksandr Bazarnov <[email protected]>

docs/connector-development/README.md

@@ -23,7 +23,7 @@ If you need support along the way, visit the [Slack channel](https://airbytehq.s
 | Tool                                                                                | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
 | ----------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
 | [Connector Builder](./connector-builder-ui/overview.md)                             | We recommend Connector Builder for developing a connector for an API source. If you’re using Airbyte Cloud, no local developer environment is required to create a new connection with the Connector Builder because you configure it directly in the Airbyte web UI. This tool guides you through creating and testing a connection. Refer to our [tutorial](./connector-builder-ui/tutorial.mdx) on the Connector Builder to guide you through the basics. |
-| [Low Code Connector Development Kit (CDK)](./config-based/low-code-cdk-overview.md) | This framework lets you build source connectors for HTTP API sources. The Low-code CDK is a declarative framework that allows you to describe the connector using a [YAML schema](./schema-reference) without writing Python code. It’s flexible enough to include [custom Python components](./config-based/advanced-topics.md#custom-components) in conjunction with this method if necessary.                                                             |
+| [Low Code Connector Development Kit (CDK)](./config-based/low-code-cdk-overview.md) | This framework lets you build source connectors for HTTP API sources. The Low-code CDK is a declarative framework that allows you to describe the connector using a [YAML schema](./schema-reference) without writing Python code. It’s flexible enough to include [custom Python components](./config-based/advanced-topics/custom-components.md) in conjunction with this method if necessary.                                                             |
 | [Python Connector Development Kit (CDK)](./cdk-python/basic-concepts.md)            | While this method provides the most flexibility to developers, it also requires the most code and maintenance. This library provides classes that work out-of-the-box for most scenarios you’ll encounter along with the generators to make the connector scaffolds for you. We maintain an [in-depth guide](./tutorials/custom-python-connector/0-getting-started.md) to building a connector using the Python CDK.                                         |
 | [Java CDK](./tutorials/building-a-java-destination.md)                              | If you're bulding a source or a destination against a traditional database (not an HTTP API, not a vector database), you should use the Java CDK instead.                                                                                                                                                                                                                                                                                                    |
 

docs/connector-development/config-based/advanced-topics/component-schema-reference.md

@@ -0,0 +1,3 @@
+# Component Schema Reference
+
+A JSON schema representation of the relationships between the components that can be used in the YAML configuration can be found [here](https://github.com/airbytehq/airbyte-python-cdk/blob/main/airbyte_cdk/sources/declarative/declarative_component_schema.yaml).

docs/connector-development/config-based/advanced-topics/custom-components.md

@@ -0,0 +1,58 @@
+# Custom Components
+
+:::info
+Please help us improve the low code CDK! If you find yourself needing to build a custom component,please [create a feature request issue](https://github.com/airbytehq/airbyte/issues/new?assignees=&labels=type%2Fenhancement%2C+%2Cneeds-triage%2C+area%2Flow-code%2Fcomponents&template=feature-request.md&title=Low%20Code%20Feature:). If appropriate, we'll add it directly to the framework (or you can submit a PR)!
+
+If an issue already exist for the missing feature you need, please upvote or comment on it so we can prioritize the issue accordingly.
+:::
+
+Any built-in components can be overloaded by a custom Python class.
+To create a custom component, define a new class in a new file in the connector's module.
+The class must implement the interface of the component it is replacing. For instance, a pagination strategy must implement `airbyte_cdk.sources.declarative.requesters.paginators.strategies.pagination_strategy.PaginationStrategy`.
+The class must also be a dataclass where each field represents an argument to configure from the yaml file, and an `InitVar` named parameters.
+
+For example:
+
+```
+@dataclass
+class MyPaginationStrategy(PaginationStrategy):
+  my_field: Union[InterpolatedString, str]
+  parameters: InitVar[Mapping[str, Any]]
+
+  def __post_init__(self, parameters: Mapping[str, Any]):
+    pass
+
+  def next_page_token(self, response: requests.Response, last_records: List[Mapping[str, Any]]) -> Optional[Any]:
+    pass
+
+  def reset(self):
+    pass
+```
+
+This class can then be referred from the yaml file by specifying the type of custom component and using its fully qualified class name:
+
+```yaml
+pagination_strategy:
+  type: "CustomPaginationStrategy"
+  class_name: "my_connector_module.MyPaginationStrategy"
+  my_field: "hello world"
+```
+
+### Custom Components that pass fields to child components
+
+There are certain scenarios where a child subcomponent might rely on a field defined on a parent component. For regular components, we perform this propagation of fields from the parent component to the child automatically.
+However, custom components do not support this behavior. If you have a child subcomponent of your custom component that falls under this use case, you will see an error message like:
+
+```
+Error creating component 'DefaultPaginator' with parent custom component source_example.components.CustomRetriever: Please provide DefaultPaginator.$parameters.url_base
+```
+
+When you receive this error, you can address this by defining the missing field within the `$parameters` block of the child component.
+
+```yaml
+  paginator:
+    type: "DefaultPaginator"
+    <...>
+    $parameters:
+      url_base: "https://example.com"
+```