Break up the model module

The `model` module has historically been one giant module re-exporting
all of the model types, which is somewhere around 100 types. This can be
a lot to look at for a new user and somewhat overwhelming, especially
with a large number of fine-grained imports from the module.

The module is now neatly split up into submodules, mostly like it has
been internally since the early versions of the library. The submodules
are:

- application
- channel
- error
- event
- gateway
- guild
- id
- invite
- misc
- permissions
- prelude
- user
- voice
- webhook

Each submodule contains types that are "owned" by the module. For
example, the `guild` submodule contains, but not limited to, Emoji,
AuditLogsEntry, Role, and Member. `channel` contains, but not limited
to, Attachment, Embed, Message, and Reaction.

Upgrade path:

Instead of glob importing the models via `use serenity::model::*;`,
instead glob import via the prelude:

```rust
use serenity::model::prelude::*;
```

Instead of importing from the root model module:

```rust
use serenity::model::{Guild, Message, OnlineStatus, Role, User};
```

instead import from the submodules like so:

```rust
use serenity::model::channel::Message;
use serenity::model::guild::{Guild, Role};
use serenity::model::user::{OnlineStatus, User};
```

1 files changed, 5 insertions, 3 deletions

diff --git a/src/model/invite.rs b/src/model/invite.rs
index 8e5c18b..ed3455c 100644
--- a/src/model/invite.rs
+++ b/src/model/invite.rs
@@ -1,5 +1,7 @@
+//! Models for server and channel invites.
+
 use chrono::{DateTime, FixedOffset};
-use super::*;
+use super::prelude::*;
 
 #[cfg(feature = "model")]
 use builder::CreateInvite;
@@ -123,7 +125,7 @@ impl Invite {
     /// Retrieve the URL for an invite with the code `WxZumR`:
     ///
     /// ```rust
-    /// # use serenity::model::*;
+    /// # use serenity::model::prelude::*;
     /// #
     /// # let invite = Invite {
     /// #     approximate_member_count: Some(1812),
@@ -289,7 +291,7 @@ impl RichInvite {
     /// Retrieve the URL for an invite with the code `WxZumR`:
     ///
     /// ```rust
-    /// # use serenity::model::*;
+    /// # use serenity::model::prelude::*;
     /// #
     /// # let invite = RichInvite {
     /// #     code: "WxZumR".to_string(),