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, 9 insertions, 7 deletions

diff --git a/src/ext/framework/configuration.rs b/src/ext/framework/configuration.rs
index 0fd18c2..b5c58c9 100644
--- a/src/ext/framework/configuration.rs
+++ b/src/ext/framework/configuration.rs
@@ -41,7 +41,7 @@ pub enum AccountType {
 /// use serenity::Client;
 /// use std::env;
 ///
-/// let mut client = Client::login_bot(&env::var("DISCORD_BOT_TOKEN").unwrap());
+/// let mut client = Client::login(&env::var("DISCORD_BOT_TOKEN").unwrap());
 ///
 /// client.with_framework(|f| f
 ///     .configure(|c| c.on_mention(true).prefix("~")));
diff --git a/src/ext/framework/create_command.rs b/src/ext/framework/create_command.rs
index 68319af..7f2c25f 100644
--- a/src/ext/framework/create_command.rs
+++ b/src/ext/framework/create_command.rs
@@ -45,7 +45,7 @@ impl CreateCommand {
     /// use serenity::model::Message;
     /// use std::env;
     ///
-    /// let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
+    /// let mut client = Client::login(&env::var("DISCORD_TOKEN").unwrap());
     ///
     /// client.with_framework(|f| f
     ///     .configure(|c| c.prefix("~"))
diff --git a/src/ext/framework/help_commands.rs b/src/ext/framework/help_commands.rs
index 4f16773..cee0e5e 100644
--- a/src/ext/framework/help_commands.rs
+++ b/src/ext/framework/help_commands.rs
@@ -10,7 +10,7 @@
 //! use serenity::Client;
 //! use std::env;
 //!
-//! let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
+//! let mut client = Client::login(&env::var("DISCORD_TOKEN").unwrap());
 //! client.with_framework(|f| f
 //!     .command("help", |c| c.exec_help(help_commands::with_embeds)));
 //! ```
diff --git a/src/ext/framework/mod.rs b/src/ext/framework/mod.rs
index 552ab93..098f26a 100644
--- a/src/ext/framework/mod.rs
+++ b/src/ext/framework/mod.rs
@@ -36,7 +36,7 @@
 //! use serenity::model::Message;
 //! use std::env;
 //!
-//! let mut client = Client::login_bot(&env::var("DISCORD_BOT_TOKEN").unwrap());
+//! let mut client = Client::login(&env::var("DISCORD_BOT_TOKEN").unwrap());
 //!
 //! client.with_framework(|f| f
 //!     .configure(|c| c.prefix("~"))
@@ -74,11 +74,13 @@ use std::default::Default;
 use std::sync::Arc;
 use std::thread;
 use ::client::Context;
-use ::model::{Channel, Message, UserId};
+use ::model::{Message, UserId};
 use ::utils;
 
 #[cfg(feature="cache")]
 use ::client::CACHE;
+#[cfg(feature="cache")]
+use ::model::Channel;
 
 /// A macro to generate "named parameters". This is useful to avoid manually
 /// using the "arguments" parameter and manually parsing types.
@@ -214,7 +216,7 @@ impl Framework {
     /// use serenity::Client;
     /// use std::env;
     ///
-    /// let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
+    /// let mut client = Client::login(&env::var("DISCORD_TOKEN").unwrap());
     /// client.with_framework(|f| f
     ///     .configure(|c| c
     ///         .depth(3)
@@ -696,7 +698,7 @@ impl Framework {
     /// use serenity::model::Message;
     /// use std::env;
     ///
-    /// let mut client = Client::login_bot(&env::var("DISCORD_TOKEN").unwrap());
+    /// let mut client = Client::login(&env::var("DISCORD_TOKEN").unwrap());
     ///
     /// client.with_framework(|f| f
     ///     .configure(|c| c.prefix("~"))