Add docs about using Basic Authentication in HTTP requests

editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request Example Basic Authentication.tid

@@ -0,0 +1,34 @@
+title: WidgetMessage: tm-http-request Example - Basic Authentication
+tags: $:/tags/Global
+
+
+!! HTTP Basic Authentication
+
+[[HTTP Basic Authentication|https://en.wikipedia.org/wiki/Basic_access_authentication]] is a simple scheme for HTTP clients pass a username and password to an HTTP server.
+
+The credentials are passed via the "Authorization" header as the string "Basic " (note the space) followed by the base64-encoded username and password joined with a colon.
+
+Here is a simple, illustrative example:
+
+```
+\procedure get-tiddler-list-from-tiddlywiki-server(url,username,password)
+	\procedure completion-get-json()
+	\import [subfilter{$:/core/config/GlobalImportFilter}]
+		<$action-log msg="In completion-get-json"/>
+		<$action-log/>
+	\end completion-get-json
+	<$action-sendmessage
+		$message="tm-http-request"
+		url=<<url>>
+		method="GET"
+		header-Authorization={{{ [<username>addsuffix[:]addsuffix<password>encodebase64[]addprefix[Basic ]] }}}
+		oncompletion=<<completion-get-json>>
+	/>
+\end get-tiddler-list-from-tiddlywiki-server
+
+<$button>
+<<get-tiddler-list-from-tiddlywiki-server url:"http://127.0.0.1:8080" username:"Joe" password:"Bloggs">>
+Download
+</$button>
+```
+