Refactor `create_and_send_new_redcap_prod_per_project_line_items.R` in preparation for service request line items.

[pbchase]

Refactor create_and_send_new_redcap_prod_per_project_line_items.R in preparation for service request line items.

• Refactor the core of create_and_send_new_redcap_prod_per_project_line_items.R into a function create_redcap_project_line_items()
• Do NOT set the id column in the function
• add tests of create_redcap_project_line_items() that use test-local data
• In create_and_send_new_redcap_prod_per_project_line_items.R replace the refactored code with the call to create_redcap_project_line_items()
• In create_and_send_new_redcap_prod_per_project_line_items.R, just before the write step, set the id column.
• Rename create_and_send_new_redcap_prod_per_project_line_items.R to send_new_invoice_line_items.R
• Fix the name of the cron job and the script it calls

[pbchase]

Instead of create_redcap_project_line_items(), let's make two functions:

get_target_projects_to_invoice <- function() {
}

get_project_service_instances <- function() {
}

Leave the write events in the ETL. That will allow data for different service_types to be bound together before the I/O.

[pbchase]

There's yet another function that can be--and should be--refactored out of the ETL. get_new_project_invoice_line_items() will make the invoice line items for new projects. This function will produce output much like that from create_service_request_line_items() described in Issue #203

[pbchase]

Addressed by PR #230