Improvement: Allow user to configure date and amount format during transaction imports

[zachgoll]

Is this issue related to a problem? Please describe.

Currently, the transaction imports feature requires users to input their data with the following convention:

• Dates: must be in ISO8601 format (i.e. YYYY-MM-DD)
• Amounts: incomes must be positive values, expenses must be negative values

Many users will be using the following flow to import data:

1. Go to bank login
2. Export transactions from bank
3. Import file to Maybe

Most bank exports will include a "date" and "amount" field, but they will all be in different formats.

The user should be able to tell Maybe what those formats are to prevent an extra step of cleaning their exported bank data prior to importing it to Maybe

Describe the work that needs to be done to address this issue

• Add fields next to "date" and "amount" fields on the "Configure" step that allow a user to select from a list of predefined formats and signage conventions