Remove selfbot support

While selfbots have always been "roughly tolerated", lately they have
been tolerated to less of a degree.

The simple answer is to no longer support selfbots in any form. This is
done for a few of reasons: 1) in anticipation of selfbots no longer
being tolerated; 2) there are few reasons why one should make a selfbot
in Rust and not a scripting language; 3) there are alternatives
(i.e. discord-rs) that still support userbots. Selfbots are simply not
a goal of the maintainer of serenity.

Upgrade path:

Don't use selfbots with serenity. Use discord-rs instead.

The following has been removed:

Enums:

- `RelationshipType`

Structs:

- `FriendSourceFlags`
- `ReadState`
- `Relationship`
- `SearchResult`
- `SuggestionReason`
- `Tutorial`
- `UserConnection`
- `UserGuildSettings`
- `UserSettings`

Removed the following fields:

- `CurrentUser::mobile`
- Ready::{
     analytics_token,
     experiments,
     friend_suggestion_count,
     notes,
     read_state,
     relationships,
     tutorial,
     user_guild_settings,
     user_settings,
 }

Removed the following methods:

- `Client::login_user`

Deprecated `Client::login_bot` in favour of `Client::login`.

Removed `client::LoginType`.

The following no longer take a `login_type` parameter:

- `Context::new`
- `Shard::new`

`Shard::sync_guilds` has been removed.

The `client::Error::{InvalidOperationAsBot, InvalidOperationAsUser}`
variants have been removed.

The following event handlers on `Client` have been removed:

- `on_friend_suggestion_create`
- `on_friend_suggestion_delete`
- `on_relationship_add`
- `on_relationship_remove`
- `on_user_guild_settings_update`
- `on_note_update`
- `on_user_settings_update`

The following `client::rest` functions have been removed:

- `ack_message`
- `edit_note`
- `get_user_connections`
- `search_channel_messages`
- `search_guild_messages`

The following `client::rest::ratelimiting::Route` variants have been
removed:

- `ChannelsIdMessagesSearch`
- `GuildsIdMessagesSearch`
- `UsersMeConnections`

The following fields on `ext::cache::Cache` have been removed:

- `guild_settings`
- `relationships`
- `settings`

while the following methods have also been removed:

- `update_with_relationship_add`
- `update_with_relationship_remove`
- `update_with_user_guild_settings_update`
- `update_with_user_note_update`
- `update_with_user_settings_update`

The following methods have been removed across models:

- `ChannelId::{ack, search}`
- `Channel::{ack, search}`
- `Group::{ack, search}`
- `GuildChannel::{ack, search}`
- `GuildId::{search, search_channels}`
- `Guild::{search, search_channels}`
- `Message::ack`
- `PartialGuild::{search, search_channels}`
- `PrivateChannel::{ack, search}`
- `UserId::{delete_note, edit_note}`
- `User::{delete_note, edit_note}`

The following events in `model::events` have been removed:

- `FriendSuggestionCreateEvent`
- `FriendSuggestionDeleteEvent`
- `MessageAckEvent`
- `RelationshipAddEvent`
- `RelationshipRemoveEvent`
- `UserGuildSettingsUpdateEvent`
- `UserNoteUpdateEvent`
- `UserSettingsUpdateEvent`

Consequently, the following variants on `model::event::Event` have been
removed:

- `FriendSuggestionCreate`
- `FriendSuggestionDelete`
- `MessageAdd`
- `RelationshipAdd`
- `RelationshipRemove`
- `UserGuildSettingUpdate`
- `UserNoteUpdate`
- `UserSettingsUpdate`

The `utils::builder::Search` search builder has been removed.

4 files changed, 53 insertions, 0 deletions

diff --git a/examples/07_sample_bot_structure/src/commands/math.rs b/examples/07_sample_bot_structure/src/commands/math.rs
new file mode 100644
index 0000000..79bfc52
--- /dev/null
+++ b/examples/07_sample_bot_structure/src/commands/math.rs
@@ -0,0 +1,5 @@
+command!(multiply(_ctx, msg, _args, one: f64, two: f64) {
+    let product = one * two;
+
+    let _ = msg.channel_id.say(&product.to_string());
+});
diff --git a/examples/07_sample_bot_structure/src/commands/meta.rs b/examples/07_sample_bot_structure/src/commands/meta.rs
new file mode 100644
index 0000000..a4036fc
--- /dev/null
+++ b/examples/07_sample_bot_structure/src/commands/meta.rs
@@ -0,0 +1,14 @@
+command!(latency(ctx, msg) {
+    let latency = ctx.shard.lock()
+        .unwrap()
+        .latency()
+        .map_or_else(|| "N/A".to_owned(), |s| {
+            format!("{}.{}s", s.as_secs(), s.subsec_nanos())
+        });
+
+    let _ = msg.channel_id.say(&latency);
+});
+
+command!(ping(_ctx, msg) {
+    let _ = msg.channel_id.say("Pong!");
+});
diff --git a/examples/07_sample_bot_structure/src/commands/mod.rs b/examples/07_sample_bot_structure/src/commands/mod.rs
new file mode 100644
index 0000000..bf58dba
--- /dev/null
+++ b/examples/07_sample_bot_structure/src/commands/mod.rs
@@ -0,0 +1,2 @@
+pub mod math;
+pub mod meta;
diff --git a/examples/07_sample_bot_structure/src/main.rs b/examples/07_sample_bot_structure/src/main.rs
new file mode 100644
index 0000000..85600eb
--- /dev/null
+++ b/examples/07_sample_bot_structure/src/main.rs
@@ -0,0 +1,32 @@
+//! Requires the 'framework' feature flag be enabled in your project's
+//! `Cargo.toml`.
+//!
+//! This can be enabled by specifying the feature in the dependency section:
+//!
+//! ```toml
+//! [dependencies.serenity]
+//! git = "https://github.com/zeyla/serenity.git"
+//! features = ["framework"]
+//! ```
+
+#[macro_use]
+extern crate serenity;
+
+mod commands;
+
+use serenity::Client;
+use std::env;
+
+fn main() {
+    let mut client = Client::login(&env::var("DISCORD_TOKEN").unwrap());
+
+    client.with_framework(|f| f
+        .configure(|c| c.prefix("~"))
+        .command("ping", |c| c.exec(commands::meta::ping))
+        .command("latency", |c| c.exec(commands::meta::latency))
+        .command("multiply", |c| c.exec(commands::math::multiply)));
+
+    if let Err(why) = client.start() {
+        println!("Client error: {:?}", why);
+    }
+}