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.Api/ApiCallBuilder.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Reflection.PortableExecutable;
+using System.Text;
+using System.Threading.Tasks;
+using Beam.Abstractions;
+
+namespace Beam {
+    public class ApiCallBuilder(HttpClient client) {
+        HttpClient Client = client;
+        string Uri;
+        object? Data;
+        object? Body;
+        HttpMethod Method = HttpMethod.Get;
+        List<KeyValuePair<string, List<string>>> Headers = [];
+        HashSet<HttpStatusCode> SuccessCodes = [HttpStatusCode.OK];
+
+        public ApiCallBuilder WithUri(string uri) {
+            Uri = uri;
+            return this;
+        }
+
+        public ApiCallBuilder WithUri(Uri uri) {
+            return WithUri(uri.AbsoluteUri);
+        }
+
+        public ApiCallBuilder WithRequestData(object? data) {
+            Data = data;
+            return this;
+        }
+
+        public ApiCallBuilder WithBody(object? data) {
+            Body = data;
+            return this;
+        }
+
+        public ApiCallBuilder WithMethod(HttpMethod method) {
+            Method = method;
+            return this;
+        }
+
+        public ApiCallBuilder WithHeaders(IEnumerable<(string Key, IEnumerable<string> Value)> headers) {
+            Headers = headers.Select((x) => new KeyValuePair<string, List<string>>(x.Key, x.Value.ToList())).ToList();
+            return this;
+        }
+
+        public ApiCallBuilder WithSuccessCodes(params HashSet<HttpStatusCode> codes) {
+            SuccessCodes = codes;
+            return this;
+        }
+
+        public ApiCallBuilder WithSuccessCodes(params IEnumerable<int> codes) {
+            SuccessCodes = codes.Cast<HttpStatusCode>().ToHashSet();
+            return this;
+        }
+
+        public ApiCallBuilder AddHeader(string key, string value) {
+            if (Headers.Any((x) => x.Key == key))
+                Headers.FirstOrDefault((x) => x.Key == key).Value.Add(value);
+            else
+                Headers.Add(new KeyValuePair<string, List<string>>(key, [value]));
+            return this;
+        }
+
+        public ApiCallBuilder AddBearer(string value)
+            => AddHeader("Authorization", "Bearer " + value);
+
+        public ApiCall Build() {
+            if (Uri is null)
+                throw new InvalidOperationException();
+            if (Method is null)
+                throw new InvalidOperationException();
+            if (Headers is null)
+                Headers = [];
+
+            return new ApiCall(Client, Uri, Method, Headers.Select((x) => new KeyValuePair<string, string[]>(x.Key, x.Value.ToArray())).ToArray(), Data, Body, SuccessCodes);
+        }
+    }
+}