[BUG]: billable-metric separator code ':'

[aelttil]

The billable metric code appears not to support the ":" separator, despite its acceptance by the user interface.
The issue does not occur with any Aggregation type. For instance, it works fine with the count type.

Steps to reproduce the behavior:

1. Go to 'billable-metric'
2. Create new billable-metric with code test:test
3. Select Aggregation type : Weighted sum
4. Add a new billable-metric into plan
5. Push new event
6. Go to customer details and show Analytics Current usage report.

Error in UI

Grafhql Query is POST http://localhost:3000/graphql

"query customerUsage($customerId: ID!, $subscriptionId: ID!) {\n customerUsage(customerId: $customerId, subscriptionId: $subscriptionId) {\n amountCents\n currency\n fromDatetime\n toDatetime\n chargesUsage {\n units\n amountCents\n charge {\n id\n invoiceDisplayName\n __typename\n }\n billableMetric {\n id\n code\n name\n __typename\n }\n filters {\n id\n __typename\n }\n groupedUsage…oiceDisplayName\n __typename\n }\n billableMetric {\n name\n __typename\n }\n filters {\n id\n amountCents\n units\n values\n invoiceDisplayName\n __typename\n }\n groupedUsage {\n amountCents\n groupedBy\n eventsCount\n units\n filters {\n id\n amountCents\n units\n values\n invoiceDisplayName\n __typename\n }\n __typename\n }\n __typename\n }\n __typename\n}"

Regards,
Alex.