10.0 add sale project fixed price task completed invoicing

[grindtildeath]

This PR is a move from OCA/sale-workflow#485

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (10.0@91a5dbf). Click here to learn what that means.
The diff coverage is 94.52%.

@@           Coverage Diff           @@
##             10.0       #4   +/-   ##
=======================================
  Coverage        ?   94.52%           
=======================================
  Files           ?        5           
  Lines           ?       73           
  Branches        ?        0           
=======================================
  Hits            ?       69           
  Misses          ?        4           
  Partials        ?        0

Impacted Files	Coverage Δ
...rice_task_completed_invoicing/models/sale_order.py	100% <100%> (ø)
...ice_task_completed_invoicing/models/procurement.py	100% <100%> (ø)
...d_price_task_completed_invoicing/models/product.py	90.9% <90.9%> (ø)
...ce_task_completed_invoicing/models/project_task.py	91.3% <91.3%> (ø)
...task_completed_invoicing/models/sale_order_line.py	92.3% <92.3%> (ø)

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[grindtildeath]

@simahawk Can we merge this as is ?