feat: SQLTarget connector instance shared with sinks

[BuzzCutNorman]

This adds a variable _target_connector to SQLTarget to house an instance of the default_sink_class.connector_class and a property to access it. The method get_sink was brought down from Target and altered to call add_sqlsink. The method add_sqlsink is a copy of the add_sink method in Target it just passes the shared connector instance to the SQLSink isntances it initalizes for each stream.

need some assistance with making this mypy compliant.

Closes #1772

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📚 Documentation preview 📚: https://meltano-sdk--1864.org.readthedocs.build/en/1864/

[edgarrmondragon]

@BuzzCutNorman can you try fixing the mypy failure? Otherwise I can take look in the coming days.

[codecov]

Codecov Report

Merging #1864 (e628032) into main (b1b3bd2) will increase coverage by 0.02%.
The diff coverage is 91.17%.

@@            Coverage Diff             @@
##             main    #1864      +/-   ##
==========================================
+ Coverage   86.87%   86.89%   +0.02%     
==========================================
  Files          59       59              
  Lines        5027     5060      +33     
  Branches      814      819       +5     
==========================================
+ Hits         4367     4397      +30     
- Misses        464      466       +2     
- Partials      196      197       +1     

Files Changed	Coverage Δ
singer_sdk/target_base.py	91.93% <91.17%> (-0.16%)	⬇️

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[BuzzCutNorman]

@edgarrmondragon I was able to get the mypy failures resolved.

[edgarrmondragon]

Thank you @BuzzCutNorman, overall this is looking great. I still have to go through the API and see how this fits with our plans for connectors (at first glance it seems it does!).

[edgarrmondragon]

It doesn't look like we need to update the cookiecutter templates, can you confirm that?

[BuzzCutNorman]

You are correct the cookiecutter templates do not need updating. In my initial version they did need to be updated. Then thanks to the sdk test I realized there was a way to accomplish this without adding a default_connector_class variable. This also means target developers won't need to make any code changes to their targets for the target to benefit from this PR.

[edgarrmondragon]

You are correct the cookiecutter templates do not need updating. In my initial version they did need to be updated. Then thanks to the sdk test I realized there was a way to accomplish this without adding a default_connector_class variable. This also means target developers won't need to make any code changes to their targets for the target to benefit from this PR.

Thanks for confirming!

[edgarrmondragon]

Thanks @BuzzCutNorman!