bmcweb: /s/boost::string_view/std::string_view/g

With boost 1.69, we get the new option, BOOST_BEAST_USE_STD_STRING_VIEW
which allows us to use std::string for all beast interfaces, instead of
boost string_view.  This was originally intended to try to reduce the
binary size, but the comparison shows only a minor improvement.

boost::string_view: 7420780 bytes
std::string_view:   7419948 bytes

832 bytes saved ! ! ! ! !

So instead, we will use the argument that it's more standard and easier
for people to grok.

Tested By:
Pulled down some bmcweb endpoints, and observed no change.  Because the
two objects are essentially drop in replacements for one another, there
should be no change.

Change-Id: I001e8cf2a0124de4792a7154bf246e3c35ef3f97
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
diff --git a/include/pam_authenticate.hpp b/include/pam_authenticate.hpp
index 7f2a33c..f211a29 100644
--- a/include/pam_authenticate.hpp
+++ b/include/pam_authenticate.hpp
@@ -17,7 +17,7 @@
     char* appPass = reinterpret_cast<char*>(appdataPtr);
     size_t appPassSize = std::strlen(appPass);
     char* pass = reinterpret_cast<char*>(malloc(appPassSize + 1));
-    if (!pass)
+    if (pass == nullptr)
     {
         return PAM_AUTH_ERR;
     }
@@ -27,7 +27,7 @@
     *resp = reinterpret_cast<pam_response*>(
         calloc(numMsg, sizeof(struct pam_response)));
 
-    if (resp == NULL)
+    if (resp == nullptr)
     {
         return PAM_AUTH_ERR;
     }
@@ -47,8 +47,8 @@
     return PAM_SUCCESS;
 }
 
-inline bool pamAuthenticateUser(const boost::string_view username,
-                                const boost::string_view password)
+inline bool pamAuthenticateUser(const std::string_view username,
+                                const std::string_view password)
 {
     std::string userStr(username);
     std::string passStr(password);