Implementation of CS3 Lock API for EOS storage driver

[gmgigi96]

No description provided.

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[glpatcern]

A few changes here and there, let's discuss them later

[lgtm-com]

This pull request introduces 2 alerts when merging 19f2b67 into 19246df - view on LGTM.com

new alerts:

• 2 for Missing error check

[lgtm-com]

This pull request introduces 2 alerts when merging ba469cd into 19246df - view on LGTM.com

new alerts:

• 2 for Missing error check

[lgtm-com]

This pull request introduces 2 alerts when merging 7a65ebe into 19246df - view on LGTM.com

new alerts:

• 2 for Missing error check

[lgtm-com]

This pull request introduces 1 alert when merging f39dbd2 into 5ba14cd - view on LGTM.com

new alerts:

• 1 for Incorrect conversion between integer types

[glpatcern]

We have tested this now and it all works fine. Some caveats to be addressed in future PRs:

• Race conditions exist in some cases, and once EOS provides an endpoint to flock a file they will be fixed.
• Attributes are currently stored on the version folder, but this can be reverted once the propagation of xattrs across versions is implemented in EOS (work in progress). This affects all xattrs, not just the locks.

Given that, the PR can be merged.

Once we reconcile with the edge branch, we could factorize out some common logic out of the decomposedfs and eosfs storage providers.