A search bar extension can display a UI component above the query bar. The component has the ability to read and write discover search bar states to enhance the search experience for users. The configuration is part of Query Enhancements.

```ts
export interface SearchBarExtensionDependencies {
  /**
   * Currently selected index patterns.
   */
  indexPatterns?: IIndexPattern[];
}

export interface SearchBarExtensionConfig {
  /**
   * The id for the search bar extension.
   */
  id: string;
  /**
   * Lower order indicates higher position on UI.
   */
  order: number;
  /**
   * A function that determines if the search bar extension is enabled and should be rendered on UI.
   * @returns whether the extension is enabled.
   */
  isEnabled: () => Promise<boolean>;
  /**
   * A function that returns the mount point for the search bar extension.
   * @param dependencies - The dependencies required for the extension.
   * @returns The mount point for the search bar extension.
   */
  getComponent: (dependencies: SearchBarExtensionDependencies) => React.ReactElement;
}

export interface QueryEnhancement {
  ...
  searchBar?: {
    ...
    extensions?: SearchBarExtensionConfig[];
  };
}

Signed-off-by: Joshua Li <joshuali925@gmail.com>
(cherry picked from commit e748e81)

…arch-project#6895)

it adds query assist specific logic in query enhancements plugin to show a UI above the PPL search bar if user has configured PPL agent.

Issues Resolved: opensearch-project#6820

* add query assist to query enhancements

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* align language to uppercase

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* pick PR 6167

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* use useState hooks for query assist

There is a bug in data explorer `AppContainer` where memorized
`DiscoverCanvas` gets unmounted after `setQuery`. PR 6167 works around
it by memorizing `AppContainer`. As query assist is no longer being
unmounted, we can use proper hooks to persist state now.

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* Revert "pick PR 6167"

This reverts commit acb0d41.

Wait for official 6167 to merge to avoid conflict

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* address comments for PR 6894

Signed-off-by: Joshua Li <joshuali925@gmail.com>

---------

Signed-off-by: Joshua Li <joshuali925@gmail.com>
(cherry picked from commit 016e0f2)

…assist (opensearch-project#6933)

* pass dependencies to isEnabled func

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* add lazy and memo to search bar extensions

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* move ppl specific string out from query assist

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* prevent setstate after hook unmounts

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* add max-height to search bar extensions

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* prevent setstate after component unmounts

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* move ml-commons API to common/index.ts

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* improve i18n and accessibility usages

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* add hard-coded suggestions for sample data indices

Signed-off-by: Joshua Li <joshuali925@gmail.com>

---------

Signed-off-by: Joshua Li <joshuali925@gmail.com>
(cherry picked from commit 4aade0f)

…ject#6972)

* disable query assist for non-default datasource

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* disable query assist input when loading

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* support MDS for query assist

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* add unit tests for agents

Signed-off-by: Joshua Li <joshuali925@gmail.com>

* Revert "add unit tests for agents"

This reverts commit 983514e.
The test configs are not yet setup in query_enhancements plugins.

Signed-off-by: Joshua Li <joshuali925@gmail.com>

---------

Signed-off-by: Joshua Li <joshuali925@gmail.com>
(cherry picked from commit 328e08e)

SearchBar extensions depend on the currently selected dataSource, which
depends on
opensearch-project#6833 to
be ported to main

Signed-off-by: Joshua Li <joshuali925@gmail.com>

Signed-off-by: Joshua Li <joshuali925@gmail.com>

To support bannar callout for query assist in un-supported languages and
notify user the feature, the search bar extensions need to be enabled
for all languages.

Signed-off-by: Joshua Li <joshuali925@gmail.com>

move SearchBarExtensions to QueryEditorExtensions and change config
settings from list to map.

Signed-off-by: Joshua Li <joshuali925@gmail.com>

Signed-off-by: Joshua Li <joshuali925@gmail.com>

Signed-off-by: Joshua Li <joshuali925@gmail.com>