Discord - Add Slash commands for botkubehelp

[PrasadG193]

Is your feature request related to a problem? Please describe.

There is no way to view BotKube help on discord

Describe the solution you'd like

https://discord.com/developers/docs/interactions/slash-commands#slash-commands-interactions-and-bot-users

The Slash commands for the discord app can be registered through HTTP endpoint using client_id and guild_it. On calling Slash command, the backend receives an interaction event. Add support in BotKube backend to respond with help message to the Slash commands

[PrasadG193]

Discord Interaction API and Slash commands are not supported by Go sdks as of now. We'll have to wait till bwmarrin/discordgo#856 gets merged.

[onedr0p]

@PrasadG193 that PR was merged.

[pkosiec]

Closing as completed as we have a dedicated @Botkube help command now, which works everywhere 🙂