required boost version is not sufficient

[kived]

The library currently requires boost 1.47 or greater according to CMakeLists.txt. I wanted to build this library on CentOS 7 (required platform, not my choice) which has boost 1.53 available by default. However, building under this version results in many errors of the form:

[5/12] Building CXX object CMakeFiles/SimpleAmqpClient.dir/src/BasicMessage.cpp.o
FAILED: CMakeFiles/SimpleAmqpClient.dir/src/BasicMessage.cpp.o 
/opt/rh/devtoolset-8/root/usr/bin/c++  -DSAC_SSL_SUPPORT_ENABLED -DSimpleAmqpClient_EXPORTS -I. -I../src -Wall -Wextra -O2 -DNDEBUG -fPIC   -std=c++98 -MD -MT CMakeFiles/SimpleAmqpClient.dir/src/BasicMessage.cpp.o -MF CMakeFiles/SimpleAmqpClient.dir/src/BasicMessage.cpp.o.d -o CMakeFiles/SimpleAmqpClient.dir/src/BasicMessage.cpp.o -c ../src/BasicMessage.cpp
../src/BasicMessage.cpp: In member function 'const string& AmqpClient::BasicMessage::ContentType() const':
../src/BasicMessage.cpp:77:33: error: 'class boost::optional<std::basic_string<char> >' has no member named 'value'
     return m_impl->content_type.value();

I was able to build with boost 1.69 instead which is available in EPEL (boost169*). I'm not sure when the c++17 compatible interface used here was added to boost but it should be somewhere between those two versions 1.53 and 1.69.

[woshilapin]

On Boost 1.55, the method optional.value() doesn't exist. On Boost 1.56, it does... but we haven't gone that far to entirely test on 1.56.