Implement CRM enterprise plan definition QoL improvements

[zoldar]

Changes

This PR adds QoL improvements to UI for creating and updating enterprise plans in CRM:

• parameters are suggest from current plan assigned to the user
• monthly pageview limit is autoformatted for readability
• numerical fields are sanitized so that only digits are considered
• whitespace is removed from input
• empty fields are treated as lack of input

Tests

• [x] Automated tests have been added