Add blocks and blocksAsString to filesUploadV2

In the API document for files.completeUploadExternal the field blocks is accepted but it cannot be added in the FilesUploadV2Request in the current slack-api-client.

I have done some changes in my fork

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

Please make sure if this topic is specific to this SDK. For general questions/issues about Slack API platform or its server-side, could you submit questions at https://my.slack.com/help/requests/new instead. 🙇

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Start with FilesUploadV2Request in the slack-api-client module and compare its fields with the files.completeUploadExternal API documentation. Review the changes in the linked fork commit for the intended shape, then verify that both blocks and blocksAsString can be supplied by the request and are represented correctly in the client.