Implemented the TemplateService service in the library target.

Test/Sources/Cases/Public/Services/TemplateServiceTests.swift

@@ -0,0 +1,47 @@
+import ColibriLibrary
+import Foundation
+import Testing
+
+struct TemplateServiceTests {
+    
+    // MARK: Properties
+    
+    private let spy = TemplateServiceSpy()
+    
+    // MARK: Functions tests
+
+    @Test(arguments: [String.content])
+    func render(_ content: String) async throws {
+        // GIVEN
+        let service = TemplateServiceMock(action: .render(content), spy: spy)
+        
+        // WHEN
+        let result = try await service.render([:], on: .template)
+        
+        // THEN
+        #expect(result == content)
+
+        #expect(spy.actions.isEmpty == false)
+    }
+    
+    @Test(arguments: [TemplateServiceError.serviceNotInitialized, .resourcePathNotFound, .templateNotFound, .contentNotRendered])
+    func render(throws error: TemplateServiceError) async throws {
+        let service = TemplateServiceMock(action: .error(error), spy: spy)
+        
+        // WHEN
+        // THEN
+        await #expect(throws: error) {
+            try await service.render([:], on: .template)
+        }
+        
+        #expect(spy.actions.isEmpty == true)
+    }
+
+}
+
+// MARK: - String+Constants
+
+private extension String {
+    static let content = ""
+    static let template = ""
+}