LOE Estimate BE and FE constarains and prepare a breakdown

Problem

To prepare a development work for the &8986 we would need to:

• Identify if we have the backend issues in place, make necessary POCs if needed
• Create frontend issues based on #4791
• Refine all the issues

Resources

Parent epic Enable a single CustomersDot User to have multi... (&8986)

[UX] Designs for Customer with multiple Account... (#4791)