[17.0][ADD] stock picking portal

[crrodrigueztrujillo]

@BinhexTeam

This module implements the following features:

• Show stock operations (pickings) in the customer portal
• Sign pickings directly in portal. Built-in Odoo signatures wizard is used
• Sharing pickings using shareable links with tokens

Users have access to the following stock operations:

• Operation type is available in portal
• User (partner) is set as "Customer"

[jelenapoblet]

@antoniodavid could you please review this one ?

[rrebollo]

@crrodrigueztrujillo Please update the PR title by changing "ADD" to "MIG". Also, mention that you’re handling the module migration in #1421. As previously stated in this thread, remember to squash the latest commits as well.