Problem Statement/Rationale

When importing a CSV which has a column where some are normal strings and others are URL slugs, for example "/Home/Example" the column gets detected as "mixed" type on import and fails with the error below as it is treated as a regular expression. 

If manually changing to String, it imports successfully.

Please be sure to attach relevant logs with any sensitive data redacted.

{"name":"BSONError","message":"The regular expression option [T] is not supported [Col 5][Row 15]"} {"name":"BSONError","message":"The regular expression option [A] is not supported [Col 5][Row 26]"} {"name":"BSONError","message":"The regular expression option [N] is not supported [Col 5][Row 28]"} {"name":"BSONError","message":"The regular expression option [S] is not supported [Col 5][Row 31]"} {"name":"BSONError","message":"The regular expression option [V] is not supported [Col 5][Row 66]"} {"name":"BSONError","message":"The regular expression option [D] is not supported [Col 5][Row 85]"} {"name":"BSONError","message":"The regular expression option [W] is not supported [Col 5][Row 86]"} {"name":"BSONError","message":"The regular expression option [C] is not supported [Col 5][Row 99]"} {"name":"BSONError","message":"The regular expression option [E] is not supported [Col 5][Row 100]"}

Steps to Reproduce

• Create a CSV
• Have a column contain text only
• in a row for that column, put values like "/Home" and "/Home/Example"
• Import the CSV in compass to an empty collection
• Notice that the field type is autodetected to mixed
• Run the import
• Notice the error that it is treated as a regular expression

Expected Results

It autodetects as string and imports successfully

Actual Results

It autodetects incorrectly and throws import errors