FINERACT-2537: Add unit tests for StreamResponseUtil

[devi-pathak2263]

Description

This PR adds unit tests for the StreamResponseUtil utility class in fineract-core.

The following functionality is covered:

• ok(StreamResponseData) response generation
• ok(AsyncResponse, StreamResponseData) asynchronous response handling
• Behavior when dispositionType is empty
• Behavior when dispositionType is present (attachment/inline)
• Correct generation of Content-Disposition headers
• Verification that StreamingOutput correctly writes the provided stream content

These tests improve code coverage and help ensure correct behavior of response streaming utilities used in the project.

JIRA: https://issues.apache.org/jira/browse/FINERACT-2537

Testing

Executed locally:

./gradlew spotlessApply
./gradlew :fineract-core:test

Checklist

Please make sure these boxes are checked before submitting your pull request - thanks!

• Write the commit message as per our guidelines
• Acknowledge that we will not review PRs that are not passing the build ("green") - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
• Create/update unit or integration tests for verifying the changes made.
• Follow our coding conventions.
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• This PR must not be a "code dump". Large changes can be made in a branch, with assistance. Ask for help on the developer mailing list.

[adamsaghy]

@devi-pathak2263 Can you please:

Set the commit email address to match with your github account email address?
Set GPG signature for commit?

[devi-pathak2263]

@devi-pathak2263 Can you please:

Set the commit email address to match with your github account email address? Set GPG signature for commit?

I have updated the commit author email to match my GitHub account and amended the commit with a GPG signature. I also updated the test imports to follow project conventions.

Please let me know if anything else needs adjustment.