Migrate over to Slash Commands

[Olian04]

Prerequisites:

• Discord.js support: feat: interactions discordjs/discord.js#5448 (merged)
• Limit command availability based on guild permission: Slash Command Permissions discord/discord-api-docs#2315 (closed, but not resolved)
• Variadic arguments (needed for Poll command): Slash Commands: add variadic arguments discord/discord-api-docs#2331 (open)

Implementation mock: (based on docs by PR #5448 author)

// The data for our command
const eventCommandData = {
  name: 'event',
  description: 'Create an event!',
  options: [{
    name: 'title',
    type: 'STRING',
    description: 'The title of the event',
    required: true,
  }],
};

client.once('ready', () => {
  // Creating a global command
  client.application.commands.create(eventCommandData);
});

client.on('interaction', interaction => {
  // If the interaction isn't a slash command, return
  if (!interaction.isCommand()) return;

  // Check if it is the correct command
  if (interaction.commandName === 'event') {
    // Get the input of the user
    const title = interaction.options[0].value;

    createEvent(interaction.channel, title);
  }
});

Possible issues:

• interaction.channel.send() might not work as normal due to the 15 minute interaction limit of Slash Commands.