Support routing SQL transactions

[mosabua]

Trino Gateway does not support a sequence of statements like the following

START TRANSACTION;
...
various statements
...
COMMIT;

Problems are:

• each statement is separate from the perspective of Trino Gateway
• on its own "START TRANSACTION" has no context that can help routing to a specific cluster
• a transaction id has to be carried through the whole sequence, but Trino Gateway does not support that

Potential ideas:

• explicit flag to enable usage, initially default to false
• implement carrying through transaction id
• figure out how failure should work if routing is possible from additional info with one or more groups and cluster (for example .. is it fine to just route to adhoc group and any cluster as long as it then continues to stick thanks to transaction id
• what do to about partial transactions without commit or rollback

[xkrogen]

This seems to relate heavily to #446 -- here we also have a problem that while in a transaction, we need sticky-routing based on some fields that the client holds/maintains.

[mosabua]

This seems to relate heavily to #446 -- here we also have a problem that while in a transaction, we need sticky-routing based on some fields that the client holds/maintains.

Agreed.

[Chaho12]

This code is out-of-date but we can refactor it to fit it to our gateway

• https://github.com/lyft/presto-gateway/pull/52/files