feat(Application): application flags

[vaporoxx]

Please describe the changes this PR makes and why it should be merged:

Adds support for the new application.flags property as of discord/discord-api-docs#2295. Since this is only sent with READY and not with Get Current Application, some parts of the lib needs a bit of restructuring:

• New property client.application – null when instantiating, a partial application as soon as READY gets emitted
• New property application.flags (obviously)
• New property application.partial
• client.fetchApplication() -> client.application.fetch()
• client.generateInvite(): Promise<string> -> string (since id is sent with READY too)
• Make now nullable properties actually nullable
• A bit of refactoring

Status

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• This PR changes the library's interface (methods or parameters added)
  • This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[NotSugden]

there should probably be info/warn tags on the description of Client#generateInvite() and the Client#application property saying they can only be used/present if the client is logged in

[vaporoxx]

there should probably be info/warn tags on the description of Client#generateInvite() and the Client#application property saying they can only be used/present if the client is logged in

I went with an error instead of adding it to the docs since that's what most methods do

Stale

[advaith1]

flags should be a BitField but unfortunately, the flags themselves haven't been documented yet and most of them aren't known (discord/discord-api-docs#2435)

[vladfrangu]

flags should be a BitField but unfortunately, the flags themselves haven't been documented yet and most of them aren't known

Yeah, and I don't know if they should be documented - I'll ask later. But, flag wise, the main ones I know off are related to the intents switches

[advaith1]

bitfield flags:

MANAGED_EMOJI = 4,
GROUP_DM_CREATE = 16,
RPC_HAS_CONNECTED = 2048,
GATEWAY_PRESENCE = 4096,
GATEWAY_PRESENCE_LIMITED = 8192,
GATEWAY_GUILD_MEMBERS = 16384,
GATEWAY_GUILD_MEMBERS_LIMITED = 32768,
VERIFICATION_PENDING_GUILD_LIMIT = 65536,
EMBEDDED = 131072

[vaporoxx]

where are those taken from? 👀

[advaith1]

the client