Builds a JSONB object from interleaved (key, value, key, value, ...)
arguments, like MySQL’s JSON_OBJECT; called with no arguments it returns
{}. Values are written into the binary directly, so they need no JSON
text escaping. Keys must be non-NULL and are converted to strings (so a
numeric key like 1 becomes "1", as in MySQL); values may be strings,
integers, floats, booleans, or NULL (rendered as JSON null). Other types —
including decimals, which JSONB numbers cannot represent exactly — are
rejected; cast them explicitly. A duplicate key keeps the last value.