Added logic for working with Tarantool schema via Box

[KaymeKaydex]

• Implemented the box.Schema() method that returns a Schema object for schema-related operations

What has been done? Why? What problem is being solved?

I didn't forget about (remove if it is not applicable):

• Tests (see documentation for a testing package)
• Changelog (see documentation for changelog format)
• Documentation (see documentation for documentation style guide)

Related issues:

[oleg-jukovec]

Please, add more unit-tests for a new requests/response. You could see how it is tested on the main package and inside the crud subpackage.

We also need examples (in example_test.go) with new features. This will help users to use the library.

Finally, we need to keep a backward compatibility until a next major release, so we need to add another Info() method with a context instead of changing the current one.

[KaymeKaydex]

Please, add more unit-tests for a new requests/response. You could see how it is tested on the main package and inside the crud subpackage.

We also need examples (in example_test.go) with new features. This will help users to use the library.

Finally, we need to keep a backward compatibility until a next major release, so we need to add another Info() method with a context instead of changing the current one.

i removed interface changes
added new examples for new methods
and added more tests to make coverage up, now all methods are covered

[KaymeKaydex]

@oleg-jukovec @DerekBum @themilchenko up

[oleg-jukovec]

Thanks for the patch. It would be nice if @dmyger paid attention to the test per function coverage.

As I could see the code is not covered (and some MessagePack unmarshal errors, but it is not critical):

Please, add a test for it.

[oleg-jukovec]

It would be nice to write a unit-test that checks whether the created circuit uses the connection passed to box.New.

[oleg-jukovec]

See comments above.

[oleg-jukovec]

Thank you for the PR! We've added some minor fixes and merged it: #446