Improving Jaybird time zone support (jdp-2020-06, jdp-2020-07, jdp-2020-09)

[Mark Rotteveel]

I want to make some improvements/changes to the time zone support
introduce in Jaybird 4.

I have created several JDPs for this:

- jdp-2020-06 OffsetTime derivation for named zone [1]

This uses 2020-01-01 as the base date for derivation instead of the
current date

- jdp-2020-09 Add ZonedDateTime support [2]

Adds support for java.time.ZonedDateTime (non-standard extension)

and (work in progress):

- jdp-2020-07 Offset conversion for named session zone [3]

Given the ambiguity of named zones, especially with CURRENT_TIME, I
want to introduce an option for Jaybird to connect using the current
time zone offset as the server time zone (even for the JVM default time
zone or explicitly specified named zone).

This could introduce minor issues during DST transitions, but overall
I think it leads to less confusion.

I would appreciate feedback or comments on these.

Mark

[1]:
https://github.com/FirebirdSQL/jaybird/blob/master/devdoc/jdp/jdp-2020-06-offsettime-derivation-for-named-zone.md
[2]:
https://github.com/FirebirdSQL/jaybird/blob/master/devdoc/jdp/jdp-2020-09-add-zoneddatetime-support.md
[3]:
https://github.com/FirebirdSQL/jaybird/blob/master/devdoc/jdp/jdp-2020-07-offset-conversion-for-named-session-zone.md
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Mark Rotteveel