Add support for block suggestion handlers

[filmaj]

Summary

This PR adds a new method available to app functions: addBlockSuggestionHandler.

It is a copy-paste of the existing Block Actions handler support, basically.

After merging this, we will have in place all of the available interactivity handlers. Thus, after this gets merged would be a good opportunity to review all the interactivity code and see how we should refactor it.

Testing

1. Pull down this branch, and point a hermes app's import_map.json to the location of this checked out branch + /src/, e.g. file:///Users/fmaj/src/deno-slack-sdk/src/
2. Add an external data source select menu to a message or view your app creates. Perhaps it can post a message that includes this in its Block Kit payload:

      {
        type: "input",
        block_id: "ext_select_block",
        optional: true,
        element: {
          type: "external_select",
          action_id: "ext_select_input",
          placeholder: {
            type: "plain_text",
            text: "Inspire",
          },
        },
        label: {
          type: "plain_text",
          text: "Inspirational Quote",
        },
      },

3. Register a block suggestion handler in your app to respond to interactions with the above drop down menu. The following example keys off of the above block kit snippet's action_id:

export default SlackFunction(...).addBlockSuggestionHandler(
  "ext_select_input", // <-- the action id of the select drop down menu
  async (args) => { // <-- `args` here should be nicely typed, and block_suggestion-specific payload bits available under `args.body`
    console.log('BLOCK SUGGESTION HANDLER, ', JSON.stringify(args.body, null, 2));
    // Fetch an inspirational quote
    const apiResp = await fetch("https://motivational-quote-api.herokuapp.com/quotes");
    const quotes = await apiResp.json();
    console.log('Returning', quotes.length, 'quotes');
    const opts = {
      "options": quotes.map((q) => ({value: `${q.id}`, text: {type:"plain_text", text: q.quote.slice(0,70)}})) // <-- watch out! options have a max text length of 75 characters
    };
    return opts;
  }
);

[codecov]

Codecov Report

Merging #116 (114cf9e) into main (4ed03f0) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #116      +/-   ##
==========================================
+ Coverage   98.45%   98.56%   +0.10%     
==========================================
  Files          46       47       +1     
  Lines        1753     1875     +122     
  Branches       93      105      +12     
==========================================
+ Hits         1726     1848     +122     
  Misses         25       25              
  Partials        2        2              

Impacted Files	Coverage Δ
...rc/functions/interactivity/block_actions_router.ts	100.00% <ø> (ø)
src/functions/interactivity/matchers.ts	100.00% <ø> (ø)
...functions/interactivity/block_suggestion_router.ts	100.00% <100.00%> (ø)
src/functions/interactivity/mod.ts	100.00% <100.00%> (ø)
src/functions/slack-function.ts	100.00% <100.00%> (ø)

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[seratch]

I forgot the exact number but we may want to mention the maximum number of options/option_groups here for more developer-friendliness

[filmaj]

I couldn't find a reference to what is the maximum number of options one can return... I did end up posting in our api docs channel about this issue: https://slack-pde.slack.com/archives/C8DPMVAQY/p1666275726696799

[shapirone]

Extremely well documented in md and in jsdoc with great test coverage. Thank you Fil! Left a couple questions/musings and nits, but nothing blocking.

[shapirone]

nit: any reason this file name is block_suggestion_types while we just use suggestion_router* elsewhere?

[filmaj]

Not really! Do you have a preference?

[shapirone]

Just to keep it consistent. I'd probably search for block_suggestion_* first, but no strong opinion

[filmaj]

@shapirone should I then rename the action_router to block_action_router, too?

[shapirone]

nit: I think we can remove this. I'm not sure there's much value in strictly typing this.