[SaaS UserCap FE] - Add Pending Members page

Description

• Introduce tabs to seat usage page (1 tab to contain current page)
• Add Pending Members tab as a second tab
• Each row in pending members would show user column and a status badge (where applicable)

Pending members can be:

• invited by email
• invited members that already have an account on SaaS

Pending members table

Issue	Concern
#333064 (closed) (👈 you're here)	It only adds the table and list the users with badges
#330027 (closed)	It adds the "Approve" button to each row in the table

Feature flag

This feature will be implemented under the saas_user_caps FF

Product description

Members that have been invited by email to a group, but haven't created an account yet, should be shown to group owners in a Pending members tab of the Billing > Seat usage page.

Design

• #321934[pending-alert.png]
• #321934[rt-group-owner-approved-awaiting-signup.png]

In this iteration, we only show the user column with the status badge -- not the approval button in the design.