Change RESPValue.init(bulk:) initializers to accept a wider range of values

Motivation:

While working to add more test coverage with `RESPTranslator`, it was made apparent that a `.bulkString(.none)` is impossible to create directly with the `RESPValue` initializers, even though it is a reasonable possibility.

Additionally, forcing all integer types to have to be stored in an `Int` is unnecessarily restrictive.

Modifications:

- Change `RESPValue.init(bulk:)` initializers to accept `Optional` instances
- Change `RESPValue.init(bulk:)` for `Int` initializer to be generic on `FixedWidthInteger`

Result:

Converting types to and from `RESPValue` should be more bi-directional and seamless.

Author: Mordil

Sources/RediStack/RESP/RESPValue.swift

@@ -39,16 +39,21 @@ public enum RESPValue {
 
     /// Initializes a `bulkString` value.
     /// - Parameter value: The `String` to store in a `.bulkString` representation.
-    public init(bulk value: String) {
-        var buffer = RESPValue.allocator.buffer(capacity: value.count)
-        buffer.writeString(value)
+    public init(bulk value: String?) {
+        guard let unwrappedValue = value else {
+            self = .bulkString(nil)
+            return
+        }
+        
+        var buffer = RESPValue.allocator.buffer(capacity: unwrappedValue.count)
+        buffer.writeString(unwrappedValue)
         self = .bulkString(buffer)
     }
 
     /// Initializes a `bulkString` value.
     /// - Parameter value: The `Int` value to store in a `.bulkString` representation.
-    public init(bulk value: Int) {
-        self.init(bulk: value.description)
+    public init<Value: FixedWidthInteger>(bulk value: Value?) {
+        self.init(bulk: value?.description)
     }
 
     /// Stores the representation determined by the `RESPValueConvertible` value.

Tests/RediStackTests/RESPTranslatorTests.swift

@@ -37,6 +37,7 @@ extension RESPTranslatorTests {
         XCTAssertTrue(writingTestPass(input: .bulkString(buffer), expected: "$5\r\n".bytes + bytes + "\r\n".bytes))
         XCTAssertTrue(writingTestPass(input: .init(bulk: "®in§³¾"), expected: "$10\r\n®in§³¾\r\n"))
         XCTAssertTrue(writingTestPass(input: .init(bulk: ""), expected: "$0\r\n\r\n"))
+        XCTAssertTrue(writingTestPass(input: .init(bulk: Optional<Int>.none), expected: "$0\r\n\r\n"))
     }
 
     func testWriting_integers() {