View existing backup codes in CMS

[brynwhyman]

Backend work implemented in #4

ACs

• Use the components created for the registration screen in Add back up code method - registration frontend #13
• Codes can be viewed by selecting a view codes action
• Back up codes are presented in a format that can be copied to the clipboard without loosing formatting.
• There is a button to download the codes using JavaScript.
• There is a button to copy the codes to the clipboard.

Designs
https://projects.invisionapp.com/share/3PNSKZQYBJZ#/screens/321186218

[brynwhyman]

We need to confirm this flow, it's not clear whether existing backup codes should be visible at any time for a user to see.

Current designs depict backup codes being visible when a user first registers an MFA method, and not again. The only functions in the CMS profile area are to reset backup codes. See https://projects.invisionapp.com/share/3PNSKZQYBJZ#/screens/321186220

[brynwhyman]

For now, #35 is preferred and will implemented instead of this issue

[robbieaverill]

My understanding is that we will never be able to view backup/recovery codes after the screen that initially generates and shows them to the user, which has already been implemented. Closing in favour of #35.