Bug in __gte for string filters

[Ian Mayo]

Describe the bug
When providing a string filter to __gte the query fails if the string contains a - character

To Reproduce
Steps to reproduce the behavior:

1. Run soul-cli, connecting to chinook.db
2. Enter this URL: http://localhost:8000/api/tables/invoices/rows?_filters=BillingAddress__gte:Theodor
3. Note that there are 21 matching records, and the first has a BillingAddress of Theodor-Heuss-Straße 34
4. Now filter for address including the hyphen: Theodor-Heuss. So a URL of: http://localhost:8000/api/tables/invoices/rows?_filters=BillingAddress__gte:Theodor-Heuss
5. Note that Soul returns an error:

{"message":"near "LIMIT": syntax error","error":{"code":"SQLITE_ERROR"}}

Note:
We seem to have a related issue with filters on InvoiceDate that contain a "-".

http://localhost:8000/api/tables/invoices/rows?_filters=InvoiceDate:2009-01-01%2000:00:00

Returns this:

{"message":"near ".01": syntax error","error":{"code":"SQLITE_ERROR"}}

Note 2:

The invoices are all dated 2009. So this query reports 412 matching records:

http://localhost:8000/api/tables/invoices/rows?_page=1&_limit=20&_filters=InvoiceDate__gt:2009

But, if I change the year to 2030, there are still 412 matching records:

http://localhost:8000/api/tables/invoices/rows?_page=1&_limit=20&_filters=InvoiceDate__gt:2030

In contrast, using a __lt operator, records are never returned:

http://localhost:8000/api/tables/invoices/rows?_page=1&_limit=20&_filters=InvoiceDate__lt:2030

These suggest __lt, __gt, __lte and __gte aren't working properly.

Separately to that, the query parsing is failing if the filter value includes a hyphen, like: 2009-01.

Expected behavior
I expected the 21 matching records to still be returned