Add code docs

Author: mythz

src/ServiceStack.Text/HttpUtils.HttpClient.cs

@@ -1010,6 +1010,9 @@ public static async Task<HttpResponseMessage> PutFileToUrlAsync(this string url,
     public static void AddHeader(this HttpRequestMessage res, string name, string value) =>
         res.WithHeader(name, value);
 
+    /// <summary>
+    /// Returns first Request Header in HttpRequestMessage Headers and Content.Headers
+    /// </summary>
     public static string? GetHeader(this HttpRequestMessage req, string name)
     {
         if (RequestHeadersResolver.TryGetValue(name, out var fn))
@@ -1026,6 +1029,10 @@ public static void AddHeader(this HttpRequestMessage res, string name, string va
     };
     public static Dictionary<string, Func<HttpResponseMessage, string?>> ResponseHeadersResolver { get; set; } = new(StringComparer.OrdinalIgnoreCase) {
     };
+    
+    /// <summary>
+    /// Returns first Response Header in HttpResponseMessage Headers and Content.Headers
+    /// </summary>
     public static string? GetHeader(this HttpResponseMessage res, string name)
     {
         if (ResponseHeadersResolver.TryGetValue(name, out var fn))
@@ -1073,6 +1080,10 @@ public static HttpRequestMessage WithHeader(this HttpRequestMessage httpReq, str
         return httpReq;
     }
 
+    /// <summary>
+    /// Populate HttpRequestMessage with a simpler, untyped API
+    /// Syntax compatible with HttpWebRequest
+    /// </summary>
     public static HttpRequestMessage With(this HttpRequestMessage httpReq, Action<HttpRequestConfig> configure)
     {
         var config = new HttpRequestConfig();
@@ -1120,6 +1131,9 @@ public static void DownloadFileTo(this string downloadUrl, string fileName,
 
 public static class HttpClientExt
 {
+    /// <summary>
+    /// Case-insensitive, trimmed compare of two content types from start to ';', i.e. without charset suffix 
+    /// </summary>
     public static bool MatchesContentType(this HttpResponseMessage res, string matchesContentType) => 
         MimeTypes.MatchesContentType(res.GetHeader(HttpHeaders.ContentType), matchesContentType);
 

src/ServiceStack.Text/HttpUtils.WebRequest.cs

@@ -1100,6 +1100,10 @@ public static HttpWebRequest WithHeader(this HttpWebRequest httpReq, string name
         return httpReq;
     }
 
+    /// <summary>
+    /// Populate HttpRequestMessage with a simpler, untyped API
+    /// Syntax compatible with HttpClient's HttpRequestMessage
+    /// </summary>
     public static HttpWebRequest With(this HttpWebRequest httpReq, Action<HttpRequestConfig> configure)
     {
         var config = new HttpRequestConfig();
@@ -1184,9 +1188,16 @@ public void UploadStream(HttpWebRequest webRequest, Stream fileStream, string fi
 
 public static class HttpClientExt
 {
+    /// <summary>
+    /// Case-insensitive, trimmed compare of two content types from start to ';', i.e. without charset suffix 
+    /// </summary>
     public static bool MatchesContentType(this HttpWebResponse res, string matchesContentType) => 
         MimeTypes.MatchesContentType(res.Headers[HttpHeaders.ContentType], matchesContentType);
-
+    
+    /// <summary>
+    /// Returns null for unknown Content-length
+    /// Syntax + Behavior compatible with HttpClient HttpResponseMessage 
+    /// </summary>
     public static long? GetContentLength(this HttpWebResponse res) =>
         res.ContentLength == -1 ? null : res.ContentLength;
 }

src/ServiceStack.Text/MimeTypes.cs

@@ -94,8 +94,9 @@ public static string GetRealContentType(string contentType)
             :  null;
     }
 
-    //Compares two string from start to ';' char, case-insensitive,
-    //ignoring (trimming) spaces at start and end
+    /// <summary>
+    /// Case-insensitive, trimmed compare of two content types from start to ';', i.e. without charset suffix 
+    /// </summary>
     public static bool MatchesContentType(string contentType, string matchesContentType)
     {
         if (contentType == null || matchesContentType == null)