Feature: Documentation via In-Console Help

[Denchick]

spqr-console=> HELP CREATE KEY RANGE;

CREATE KEY RANGE - creates a key range for query routing

Syntax:
  CREATE KEY RANGE <id> FROM <bound> ROUTE TO <shard> FOR DISTRIBUTION <dist>

Examples:
  -- For integer distribution:
  CREATE KEY RANGE kr1 FROM 0 ROUTE TO shard1 FOR DISTRIBUTION users;
  CREATE KEY RANGE kr2 FROM 1000000 ROUTE TO shard2 FOR DISTRIBUTION users;

  -- For VARCHAR HASH (MURMUR):
  -- MURMUR hashes to uint32 (0..4294967295)
  CREATE KEY RANGE kr1 FROM 0 ROUTE TO shard1 FOR DISTRIBUTION answers;
  CREATE KEY RANGE kr2 FROM 2147483648 ROUTE TO shard2 FOR DISTRIBUTION answers;

Tip: Use CREATE KEY RANGES AUTO for automatic distribution.

Related to: #1887

[Denchick]

We discussed this issue with @reshke.

Although the proposed behavior is not exactly aligned with the typical psql approach, we still think it provides practical value. We are going to implement it.

The exact implementation details are not decided yet, so this will be addressed incrementally as we design the solution.