add db migration for varying bitrate for audio recording

[ebubae]

Is your feature request related to a problem? Please describe.
We want to be able to vary bitrates for certain mobile users whose device struggle with high bitrate audio recording.

Describe the solution you'd like
Update the DB to store the default 30k bitrate for old recording to allow for future recordings to have a lower bitrate. This will include updating bytes calculation to include the variable bit rate number.

Describe alternatives you've considered
Using alternative mic recorder solutions with noise/echo cancellation.