Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. It would be nice to have [...]
Currently, csv processor doesn't support multiple line input. It is good to support multi-line csv input where first line is the header line.

Describe the solution you'd like
Add an option to CSV processor to parse multi-line input. The suggested config is

processor:
   - csv:
       <existing options>
       - multi_line : true   # default false

When multi_line is specified, key and keys` are optional

Describe alternatives you've considered (Optional)
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.