Add isConnected property to RedisClient protocol

Motivation:

It it pretty common as a developer when working with connections and "database" clients to want to know
if the connection is currently open before doing any work.

Modifications:

Add `var isConnected: Bool { get }` requirement to the `RedisClient` protocol

Result:

Developers should now have access to the connectivity state of any `RedisClient`

Author: Mordil

Sources/RediStack/RedisClient.swift

@@ -23,7 +23,10 @@ import NIO
 ///
 /// See [https://redis.io/commands](https://redis.io/commands)
 public protocol RedisClient {
-    /// The `EventLoop` that this client operates on.
+    /// Is the client currently connected to Redis?
+    var isConnected: Bool { get }
+    
+    /// The `NIO.EventLoop` that this client operates on.
     var eventLoop: EventLoop { get }
 
     /// The `Logging.Logger` that this client uses.
@@ -33,7 +36,7 @@ public protocol RedisClient {
     /// - Parameters:
     ///     - command: The command to execute.
     ///     - arguments: The arguments, if any, to be sent with the command.
-    /// - Returns: An `EventLoopFuture` that will resolve with the Redis command response.
+    /// - Returns: A `NIO.EventLoopFuture` that will resolve with the Redis command response.
     func send(command: String, with arguments: [RESPValue]) -> EventLoopFuture<RESPValue>
 
     /// Updates the client's logger.
@@ -44,7 +47,7 @@ public protocol RedisClient {
 extension RedisClient {
     /// Sends the desired command without arguments.
     /// - Parameter command: The command keyword to execute.
-    /// - Returns: An `EventLoopFuture` that will resolve with the Redis command response.
+    /// - Returns: A `NIO.EventLoopFuture` that will resolve with the Redis command response.
     public func send(command: String) -> EventLoopFuture<RESPValue> {
         return self.send(command: command, with: [])
     }

Sources/RediStack/RedisConnection.swift

@@ -105,7 +105,6 @@ public final class RedisConnection: RedisClient {
         }
     }
     public var eventLoop: EventLoop { return self.channel.eventLoop }
-    /// Is the connection to Redis still open?
     public var isConnected: Bool {
         // `Channel.isActive` is set to false before the `closeFuture` resolves in cases where the channel might be
         // closed, or closing, before our state has been updated