Autodetect MCAP in rosbag2_cpp open

[doisyg]

Description

Ongoing discussion with @clalancette here: ros2/cartographer_ros#67
Should rosbag automatically detects the bag format in the open method here ?

rosbag2/rosbag2_cpp/include/rosbag2_cpp/reader.hpp

Lines 64 to 78 in c611a80

	/**
	* Opens an existing bagfile and prepare it for reading messages.
	* The bagfile must exist.
	* This must be called before any other function is used.
	*
	* \note This will open URI with the default storage options
	* * using sqlite3 storage backend
	* * using no converter options, storing messages with the incoming serialization format
	* \sa rmw_get_serialization_format.
	* For specifications, please see \sa open, which let's you specify
	* more storage and converter options.
	*
	* \param storage_uri URI of the storage to open.
	**/
	void open(const std::string & uri);

And if yes, how ? Doing it based the file extension ?

Related:

• Same for python api ?
• Same for ros2 bag play cli ? (instead of passing the -s flag)

[MichaelOrlov]

@doisyg @clalancette MCAP or SQLite3 bags auto detection has already been done in #1072
It's already works for ros2 bag play

As regards to the aforementioned void open(const std::string & uri); CPP and Python API - will need to make one line fix
in

rosbag2/rosbag2_cpp/src/rosbag2_cpp/reader.cpp

Line 42 in c611a80

storage_options.storage_id = "sqlite3";

remove entire line with storage_options.storage_id = "sqlite3"; initialization.
If storage_options.storage_id is an empty string - SequentialReader will try to auto-detect storage plugin by file extension.

[emersonknapp]

I just ran into this myself and have a solution in #1167