Use nested namespace

Nested namespace is introduced in C++ 17. This saves nearly 50 lines.
This change also puts tests into a nested namespace, which saves
unnecessary using directives.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I7c3e38588fd5c2cbd83ac13ee24327318e8c06a4
diff --git a/bmc-vmi-ca/ca_cert_entry.cpp b/bmc-vmi-ca/ca_cert_entry.cpp
index 94c0a25..f4d7b2e 100644
--- a/bmc-vmi-ca/ca_cert_entry.cpp
+++ b/bmc-vmi-ca/ca_cert_entry.cpp
@@ -4,9 +4,7 @@
 

 #include "ca_certs_manager.hpp"

 

-namespace ca

-{

-namespace cert

+namespace ca::cert

 {

 

 void Entry::delete_()

@@ -14,5 +12,4 @@
     // Remove entry D-bus object

     manager.erase(id);

 }

-} // namespace cert

-} // namespace ca

+} // namespace ca::cert

diff --git a/bmc-vmi-ca/ca_certs_manager.cpp b/bmc-vmi-ca/ca_certs_manager.cpp
index 3b11a53..0f4e908 100644
--- a/bmc-vmi-ca/ca_certs_manager.cpp
+++ b/bmc-vmi-ca/ca_certs_manager.cpp
@@ -9,9 +9,7 @@
 #include <phosphor-logging/log.hpp>
 #include <xyz/openbmc_project/Common/error.hpp>
 
-namespace ca
-{
-namespace cert
+namespace ca::cert
 {
 static constexpr auto maxCertSize = 4096;
 namespace fs = std::filesystem;
@@ -66,5 +64,4 @@
     }
 }
 
-} // namespace cert
-} // namespace ca
+} // namespace ca::cert
diff --git a/bmc-vmi-ca/ca_certs_manager.hpp b/bmc-vmi-ca/ca_certs_manager.hpp
index a1db918..21088b6 100644
--- a/bmc-vmi-ca/ca_certs_manager.hpp
+++ b/bmc-vmi-ca/ca_certs_manager.hpp
@@ -8,9 +8,7 @@
 #include <sdbusplus/server/object.hpp>
 #include <sdeventplus/source/event.hpp>
 
-namespace ca
-{
-namespace cert
+namespace ca::cert
 {
 
 class CACertMgr;
@@ -74,5 +72,4 @@
     uint32_t lastEntryId;
 };
 
-} // namespace cert
-} // namespace ca
+} // namespace ca::cert