Recorder Pending count (#637)

[omgoo]

• recorder: add pending counter (in redis) to when using redis based dedup system, supports User Display Name Support + Token Refresh Support webrecorder/browsertrix#44

Description

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Replay fix (fixes a replay specific issue)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added or updated tests to cover my changes.
• All new and existing tests passed.