Add option to specify the AWS region

[paroga]

Fixes #8

[mkgrgis]

@paroga , what about regression tests? This pgspider FDW projects usually means time budget as 10-15% of coding, 65-80% of tests and 10-15% of discussing. Please refer testing and coding components in this commit as example.

[paroga]

@paroga , what about regression tests? This pgspider FDW projects usually means time budget as 10-15% of coding, 65-80% of tests and 10-15% of discussing. Please refer testing and coding components in this commit as example.

i don't see how this is testable with a local DynamoDB setup, but please feel free to suggest a good idea.

BTW: can you give me some insight on running the current tests in general? i'm not able to get the current ones running correctly on a current Debian and/or Alpine Linux distribution. What's the "correct" system to run the tests on? E.g. it looks like the error messages of curl do not match on my system: ERROR: dynamodb_fdw: failed to execute remote SQL: curlCode: 7, Couldn't connect to server vs. ERROR: dynamodb_fdw: failed to execute remote SQL: curlCode: 7, Could not connect to server (Couldn't vs Could not)

[mkgrgis]

i don't see how this is testable with a local DynamoDB setup, but please feel free to suggest a good idea.

Just option test and SELECT from PostgreSQL information schema without any outer effects. This allows minimal ensure your contribution will exist after some future PRs.