Package validation

Early error detection simplifies application development, troubleshooting and support. Currently Murano does not provide mechanisms to perform validation of the Murano application package before running deployment process. Thus Murano cannot prevent uploading of invalid package and developer cannot verify that application package contains valid structure and code before deployment process. Many problems with application packages (such as invalid package structure, errors in code, typos, etc.) can be detected and solved by using static validation tool.

A new toolkit for validation MuranoPL language and Murano application packages should be introduced. Key points:

 - The toolkit SHOULD be implemented as a standalone Python package (library) with CLI interface.
 - Validation library will be used to validate Murano packages during loading process.
 - CLI tool can be used by application developer to perform early checks before package is assembled.
 - Toolkit should be extensible with custom validators. It will provide API for extension purposes.
 - Toolkit should be configurable to run list of specified inspections or to ignore specified inspections.

Toolkit should implement the following validation suites:
 - Manifest validation
 - Classes validation
 - UI definition validation

Other validators can be implemented later as part of this tool or as external packages