refactor: modularize Beam into new projects and interfaces

- Introduced modularity by splitting Beam into new projects: Beam.Abstractions, Beam.Models, and Beam.Downloaders.
- Refactored existing classes into appropriate namespaces and projects.
- Replaced specific implementations with abstractions (e.g., SourceLinkBuilder to LinkBuilder, State to IState, etc.).
- Updated interfaces: added ITemplate, IArticleData, IDownloadReport, and others for improved extensibility.
- Removed deprecated classes like SourceLinkBuilder and StateChangerFactory.
- Enhanced link handling in downloaders by refactoring to use `string` over `SourceLink`.
- Consolidated shared logic under Beam.Abstractions.

Beam.Tests/SouceLinkBuilder.Tests.cs

@@ -3,35 +3,36 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using Beam.Data;
 
 namespace Beam.Tests {
     public class SouceLinkBuilder {
         [Fact]
         public void ShouldConstruct_NoErrors() {
-            _ = new SourceLinkBuilder("example.com");
+            _ = new LinkBuilder("example.com");
         }
         [Fact]
         public void ShouldBuild_NoErrors() {
-            _ = new SourceLinkBuilder("example.com").Build();
+            _ = new LinkBuilder("example.com").Build();
         }
         [Fact]
         public void ShouldBuild_Correctly() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             var link = k.Build();
-            Assert.Equal("https://example.com/", link.Link.ToString()); // trailing slash for RFC standardization stuff
+            Assert.Equal("https://example.com/", link); // trailing slash for RFC standardization stuff
         }
         [Fact]
         public void ShouldBuild_SegmentAddsCorrectly() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             k.AddSegment("folder1");
             var link = k.Build();
-            Assert.Equal("https://example.com/folder1", link.Link.ToString());
+            Assert.Equal("https://example.com/folder1", link);
         }
         [Fact]
         public void ShouldThrow_EmptySegmentsDisallowed() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             Assert.Throws<ArgumentException>(() => {
                 k.AddSegment("");
@@ -41,7 +42,7 @@ namespace Beam.Tests {
         [InlineData("folder1", "folder2", "folder3")]
         [InlineData("f1", "f5", "f6")]
         public void ShouldBuild_MultipleSegmentsCorrect(params string[] segments) {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             foreach (var segment in segments) {
                 k.AddSegment(segment);
@@ -58,34 +59,34 @@ namespace Beam.Tests {
 
             var link = k.Build();
 
-            Assert.Equal(builder.ToString(), link.Link.ToString());
+            Assert.Equal(builder.ToString(), link);
         }
         [Fact]
         public void ShouldBuild_SingleParameterCorrect() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             k.AddSegment("f1");
             k.AddParameters(0, "?q=");
             var link = k.Build("foo");
-            Assert.Equal("https://example.com/f1?q=foo", link.Link.ToString());
+            Assert.Equal("https://example.com/f1?q=foo", link);
         }
         [Fact]
         public void ShouldBuild_MultiParameterCorrect() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             k.AddSegment("f1");
             k.AddParameters(0, "?q=", "?m=");
             var link = k.Build("foo", "bar");
-            Assert.Equal("https://example.com/f1?q=foo?m=bar", link.Link.ToString());
+            Assert.Equal("https://example.com/f1?q=foo?m=bar", link);
         }
         [Fact]
         public void ShouldBuild_MultiParameterCorrectWithSuffix() {
-            var k = new SourceLinkBuilder("example.com");
+            var k = new LinkBuilder("example.com");
             Assert.NotNull(k);
             k.AddSegment("f1", "&");
             k.AddParameters(0, "?q=", "?m=");
             var link = k.Build("foo", "bar");
-            Assert.Equal("https://example.com/f1?q=foo&?m=bar", link.Link.ToString());
+            Assert.Equal("https://example.com/f1?q=foo&?m=bar", link);
         }
 
     }