ignore case of with header row in sql when creating external table

[dylankyc]

Resolves #1242

Currently, creating an external table using datafusion-cli with this sql:

CREATE EXTERNAL TABLE t(c1 int) STORED AS CSV with header row LOCATION 'foo.csv'

will fail when with header row tokens are in lower case. This pr is a fix.

[alamb]

Looks good to me. Thank you @lichuan6

[alamb]

@lichuan6 there appears to be some failures on the CI checks

[dylankyc]

@lichuan6 there appears to be some failures on the CI checks

OK, thanks @alamb for pointing it out. It seems using self.consume_token(&Token::make_keyword("WITH")) will only recognize upper case keyword. What's the best way to do case-insensitive token parsing?

Currently, after changing signature from

fn consume_token(&mut self, expected: &str) -> bool

to

fn consume_token(&mut self, expected: &Token) -> bool

to do case-insensitive parsing, I created a new Token::Word enum with upper case of next token. Don't know if this is the best practice.

[dylankyc]

@Dandandan Could you please approve and make the tests run?

[alamb]

Looks good to me. Thank you @lichuan6

Any thoughts @Dandandan ?

[dylankyc]

Hi, @Dandandan Could you please review this PR?

[alamb]

If @Dandandan doesn't have anything to add I'll plan to merge this PR tomorrow

[alamb]

Thanks again @lichuan6