Function parse_steps 

pub fn parse_steps(defs: &[Value]) -> Result<StepChain, OversyncError>

Parse a JSON array of step definitions into a StepChain.

Each element must be an object with a type field and step-specific parameters.

Supported types

type	params
rename	from, to
set	field, value
upper	field
lower	field
remove	field
copy	from, to
default	field, value
filter	field, op, value
map_value	field, mapping
truncate	field, max_len
nest	fields, into
flatten	field
hash	field
coalesce	fields, into