Add author_subname type

[mztnnrt]

Hello! I would like to start by expressing my sincere appreciation for your consistent contributions to this project.
Thank you so much!

Summary

Add author_subname for message, the section indicated by the arrow.

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Other language API Client ex. slack-go/slack

https://github.com/slack-go/slack/blob/c4095cb17cf21c2b2b9c459d5512d14ca5143f64/attachments.go#L70-L71

AuthorName    string `json:"author_name,omitempty"`
AuthorSubname string `json:"author_subname,omitempty"`

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Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @mztnnrt to sign the Salesforce Inc. Contributor License Agreement.

[mwbrooks]

Hey @mztnnrt 👋🏻

Thanks a bunch for the pull request 🙇🏻 It's wonderful to hear that you've finding the project helpful and we always appreciate pull requests that continue to improve the project for everyone!

I'll be honest, I didn't know the author_subname property existed! Digging a little deeper, it appears to be a legacy property for message attachments. It's not documented on api.slack.com, which is probably why we have not added the type definition to the SDK.

Regardless, for those in-the-know, the property is still supported by message attachments and displays correctly in Slack. It's quite slick!

How do the other maintainer's feel about adding this type? It seems good to me.

[mztnnrt]

Hi @mwbrooks, Thanks your reply ! 🙏

It's not documented on api.slack.com,

Yes ! In fact, I also don't know how long Slack will support author_subname, but now I think it useful for display_id and so on.
Therefore, i also feel good to add it. I think it is good to consider it positively.

[seratch]

@mwbrooks

How do the other maintainer's feel about adding this type? It seems good to me.

I also think this is a good addition 👍 We may want to add the field here too, but missing it there at this moment doesn't necessarily prevent us from adding the actually working thing to the SDKs.

I can work on Python/Java SDKs later on.

[seratch]

My updates on this:

• Java SDK already has it: https://github.com/slackapi/java-slack-sdk/blob/v1.29.2/slack-api-model/src/main/java/com/slack/api/model/Attachment.java#L81-L82
• PR to the Python SDK: Add author_subname to attachment models python-slack-sdk#1366

[mztnnrt]

Hi @seratch 👋 Thanks for your adjustment about this subname!
Please continue your support 🙏

^{P.S. I always read your article qiita.com about Slack and it's very useful, thanks.}