Enable arbitrary posting for fetchpost -> new command: fetchpostj

[andrejohansson]

Is your feature request related to a problem? Please describe.
When using fetchpost today the data is sent form encoded and with the header application/x-www-form-urlencoded. It would be nice if we could send arbitrary content headers and arbritrary content data instead.

For example, posing a json payload per csv row to the endpoint and setting content type header to application/json. I know I can set headers today but I cannot change the posted data format.

Describe the solution you'd like

1. Add a parameter to let us define a payload template, for example in mustcache format (or handlebar or other template language)
2. Expose all csv row columns as variables (eg. column country can be used in template as {{country}}
3. For each csv row, render the template and post it

[jqnatividad]

This is an interesting feature request @andrejohansson and can appreciate its utility.

I'll add it to the backlog.

[jqnatividad]

This will be implemented as the new fetchpostj command.

[github-actions]

Stale issue message

[jqnatividad]

Reopening... still planned, just need time... bad github-actions bot!

[github-actions]

Stale issue message

[jqnatividad]

Just to close the loop on this one - there is no need for a new fetchpostj command.

fetchpost can now post just about any content-type, so long as the requisite MiniJinja template is created for it.