BOOKKEEPER-922: CreaterId in ledger metadata

Introduces a generic Map<String, byte[]> customMetadata to be stored as part of ledger metadata on the metadata server(zk).

Author: Rithin Shetty <rithingmail.com>

Author: Rithin <rithin.shetty@salesforce.com>

Reviewers: Enrico Olivelli <eolivelli@gmail.com>, Sijie Guo <sijie@apache.org>

Closes #46 from rithin-shetty/JIRA-922-ledgerCustomMetadata
7 files changed