Prepare for boost::url upgrade

The new boost URL now interops properly with std::string_view, which is
great, and cleans up a bunch of mediocre code to convert one to another.
It has also been pulled into boost-proper, so we no longer need a
boost-url dependency that's separate.

Unfortunately, boost url makes these improvements by changing
boost::string_view for boost::urls::const_string, which causes us to
have some compile errors on the missing type.

The bulk of these changes fall into a couple categories, and have to be
executed in one commit.
string() is replaced with buffer() on the url and url_view types
boost::string_view is replaced by std::string_view for many times, in
many cases removing a temporary that we had in the code previously.

Tested: Code compiles with boost 1.81.0 beta.
Redfish service validator passes.
Pretty good unit test coverage for URL-specific use cases.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I8d3dc89b53d1cc390887fe53605d4867f75f76fd
diff --git a/test/http/utility_test.cpp b/test/http/utility_test.cpp
index 58a2865..2e0c82e 100644
--- a/test/http/utility_test.cpp
+++ b/test/http/utility_test.cpp
@@ -84,16 +84,16 @@
 TEST(Utility, UrlFromPieces)
 {
     boost::urls::url url = urlFromPieces("redfish", "v1", "foo");
-    EXPECT_EQ(std::string_view(url.data(), url.size()), "/redfish/v1/foo");
+    EXPECT_EQ(url.buffer(), "/redfish/v1/foo");
 
     url = urlFromPieces("/", "badString");
-    EXPECT_EQ(std::string_view(url.data(), url.size()), "/%2f/badString");
+    EXPECT_EQ(url.buffer(), "/%2F/badString");
 
     url = urlFromPieces("bad?tring");
-    EXPECT_EQ(std::string_view(url.data(), url.size()), "/bad%3ftring");
+    EXPECT_EQ(url.buffer(), "/bad%3Ftring");
 
     url = urlFromPieces("/", "bad&tring");
-    EXPECT_EQ(std::string_view(url.data(), url.size()), "/%2f/bad&tring");
+    EXPECT_EQ(url.buffer(), "/%2F/bad&tring");
 }
 
 TEST(Utility, readUrlSegments)
@@ -232,7 +232,7 @@
 
     appendUrlPieces(url, "/", "bad&tring");
     EXPECT_EQ(std::string_view(url.data(), url.size()),
-              "/redfish/v1/foo/bar/%2f/bad&tring");
+              "/redfish/v1/foo/bar/%2F/bad&tring");
 }
 
 } // namespace