some security and bug fixes

Merge pull request #28 from rchincha/log-fix

log: fix appending to logs

add LDAP authN support

add LDAP authN support
increase code coverage with UT

NOTE: This is a pre-release, pls don't use in production.

some tls improvements

Merge pull request #16 from rchincha/tls

tls: harden TLS path

v0.2.8 - TLS auth and build-in-container

• tls: require mutual auth only when htpasswd not available
• support building in a docker container

Add multiple level tags

This update has the support for hierarchical tags for images like zot.org/zot:1.1.1 and cisco.com/zot/client:1.0.0

v0.2.6: Merge pull request #8 from rchincha/master

routes: fix error codes