Add managed identity support to EventGridOutput

[Arnab Nandy (arnabnandy7)]

Description

Adds managed identity support to the Java EventGridOutput annotation.

The Event Grid extension supports identity-based authentication through the connection property, but this property was not exposed by the Java annotation. Additionally, the key-based properties were mandatory, preventing users from configuring the annotation exclusively with connection.

Fixes #220.

Changes

• Added an optional connection property to EventGridOutput.
• Made topicEndpointUri optional.
• Made topicKeySetting optional.
• Added a test covering the identity-based annotation contract.

Users can now configure managed identity authentication as follows:

@EventGridOutput(
    name = "outputEvent",
    connection = "MyEventGridConnection")
OutputBinding<String> outputEvent

The corresponding application setting uses the connection prefix:

MyEventGridConnection__topicEndpointUri

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