Add TextPlainParameters to support sending plain text request body

Documentation/APIKit2MigrationGuide.md

@@ -77,6 +77,7 @@ APIKit provides 3 parameters types that conform to `BodyParametersType`:
 - [**Added**] `class JSONBodyParameters`
 - [**Added**] `class FormURLEncodedBodyParameters`
 - [**Added**] `class MultipartFormDataBodyParameters`
+- [**Added**] `class TextPlainParameters`
 
 ### HTTP Headers
 

Documentation/ConvenienceParametersAndActualParameters.md

@@ -94,3 +94,4 @@ APIKit provides 3 body parameters type listed below:
 |`JSONBodyParameters`             |`Any`                                   |
 |`FormURLEncodedBodyParameters`   |`[String: Any]`                         |
 |`MultipartFormDataBodyParameters`|`[MultipartFormDataBodyParameters.Part]`|
+|`TextPlainParameters`            |`String`                                |

Sources/APIKit/BodyParameters/TextPlainParameters.swift

@@ -0,0 +1,23 @@
+import Foundation
+
+/// `TextPlainParameters` serializes plain text for HTTP body and states its content type is plain text.
+public struct TextPlainParameters: BodyParameters {
+   /// The plain text to be serialized.
+   private let text: String
+
+   /// Returns `TextPlainParameters` that is initialized with plain text.
+   public init(text: String) {
+       self.text = text
+   }
+
+   // MARK: - BodyParameters
+   /// `Content-Type` to send. The value for this property will be set to `Accept` HTTP header field.
+   public var contentType: String {
+       "text/plain"
+   }
+
+   /// Builds `RequestBodyEntity.data` that represents plain text.
+   public func buildEntity() throws -> RequestBodyEntity {
+       .data(Data(self.text.utf8))
+   }
+}

Tests/APIKitTests/BodyParametersType/TextPlainParametersTests.swift

@@ -0,0 +1,50 @@
+import Foundation
+import XCTest
+import APIKit
+
+class TextPlainParametersTests: XCTestCase {
+    func testTextPlainSuccess() throws {
+       let text = "Hello, World!"
+       let parameters = TextPlainParameters(text: text)
+
+       XCTAssertEqual(parameters.contentType, "text/plain")
+
+       guard case .data(let data) = try parameters.buildEntity() else {
+           XCTFail()
+           return
+       }
+
+       let decodedText = String(data: data, encoding: .utf8)
+       XCTAssertEqual(decodedText, text)
+    }
+
+    func testTextPlainEmpty() throws {
+       let text = ""
+       let parameters = TextPlainParameters(text: text)
+
+       XCTAssertEqual(parameters.contentType, "text/plain")
+
+       guard case .data(let data) = try parameters.buildEntity() else {
+           XCTFail()
+           return
+       }
+
+       let decodedText = String(data: data, encoding: .utf8)
+       XCTAssertEqual(decodedText, text)
+    }
+
+    func testTextPlainUnicode() throws {
+        let text = "Hello, World! 😄🌍"
+        let parameters = TextPlainParameters(text: text)
+
+        XCTAssertEqual(parameters.contentType, "text/plain")
+
+        guard case .data(let data) = try parameters.buildEntity() else {
+            XCTFail()
+            return
+        }
+
+        let decodedText = String(data: data, encoding: .utf8)
+        XCTAssertEqual(decodedText, text)
+    }
+}