Bolt V3 support & transaction configuration

[lutovich]

Bolt V3 allows additional metadata to be attached to BEGIN and RUN messages. This makes it possible to expose a couple new features in the API.

Auto-commit transactions executed via Session#run() now support bookmarks. In previous protocol versions, there was no good place in the RUN message to attach bookmarks. Auto-commit transactions will now use bookmarks given in Driver#session(bookmarkOrBookmarks) function and participate in causal chaining within a session.

Transactions functions, auto-commit, and explicit transactions now accept a configuration object with transaction timeout and metadata. Example of a configuration object:

{
    timeout: 3000, // 3 seconds
    metadata: {key1: 42, key2: '42'}
}

where timeout is specified in milliseconds and metadata is an object containing valid Cypher types.

Transactions that execute longer than the configured timeout will be terminated by the database. This functionality allows limiting query/transaction execution time. Specified timeout overrides the default timeout configured in the database using dbms.transaction.timeout setting. Examples:

Specified transaction metadata will be attached to the executing transaction and visible in the output of dbms.listQueries and dbms.listTransactions procedures. It will also get logged to the query.log. This functionality makes it easier to tag transactions and is equivalent to dbms.setTXMetaData procedure.

Examples:

var driver = neo4j.driver(...);
var session = driver.session();

var txConfig = {
  timeout: 5000, // 5 seconds
  metadata: {
    type: 'My Query',
    application: 'My App #1',
    sequence_number: 42
  }
};

// transaction configuration for auto-commit transaction
session.run('RETURN $x', {x: 42}, txConfig)
       .then(...)
       .catch(...)

// transaction configuration for explicit transaction
var tx = session.beginTransaction(txConfig);
tx.run(...);

// transaction configuration for read transaction function
session.readTransaction(tx => tx.run('RETURN $x', {x: 42}), txConfig)
       .then(...)
       .catch(...)

// transaction configuration for write transaction function
session.writeTransaction(tx => tx.run('RETURN $x', {x: 42}), txConfig)
       .then(...)
       .catch(...)