Keep field name for csv timestamp column (don't implicitly convert)

[stephanie-engel]

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

Root Cause Analysis:
Within the csv parser, the field name for the csv_timestamp_column is, initially, converted from a string into an int. This causes the field name (for example: 202011131605) to be interpreted as a Unix format (instead of the Go reference time 200601021504).

The Fix:

• Prevent implicit type conversion on the timestamp column, so that parseTimestamp can correctly parse the time as unix or UTC
• Added a unit test to verify TimestampFormat: "200601021504"

closes #7288

[srebhan]

Hey @stephanie-engel, nice work! However, I think we also have to handle the cases where the column-type is given explicitly. This is the section above your change. How about handling both cases by adding

		if fieldName == p.TimestampColumn {
				recordFields[fieldName] = value
                                continue
                }

directly before line 208

			if len(p.ColumnTypes) > 0 {

This way you can leave the lines 241--250 unchanged.

[stephanie-engel]

Hey @stephanie-engel, nice work! However, I think we also have to handle the cases where the column-type is given explicitly. This is the section above your change. How about handling both cases by adding

		if fieldName == p.TimestampColumn {
				recordFields[fieldName] = value
                                continue
                }

directly before line 208

			if len(p.ColumnTypes) > 0 {

This way you can leave the lines 241--250 unchanged.

Thanks for the great feedback, @srebhan ! I just went ahead and made the changes you requested. I confirmed that the timestamp is still parsed correctly and the unit tests still pass 😄

[ssoroka]

Looks great, congratulations. 🥇