samples: add samples for tagging feature

[mayurkale22]

Adds a sample for assigning and querying tags.

Follow-up to #576

Note: We will add the test when the feature is fully available.

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/src/main/java/com/example/spanner/TransactionWithTagSample.java:31, tag spanner_set_transaction_tag
• samples/snippets/src/main/java/com/example/spanner/TransactionWithTagSample.java:78, tag spanner_set_request_tag

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[codecov]

Codecov Report

Merging #1042 (a558647) into master (0bc9972) will increase coverage by 0.05%.
The diff coverage is n/a.

❗ Current head a558647 differs from pull request most recent head 9ad4e41. Consider uploading reports for the commit 9ad4e41 to get more accurate results

@@ Coverage Diff @@ ## master #1042 +/- ## ============================================ + Coverage 85.18% 85.24% +0.05%  - Complexity 2640 2658 +18  ============================================ Files 155 155 Lines 14413 14453 +40 Branches 1348 1362 +14 ============================================ + Hits 12278 12320 +42  + Misses 1567 1565 -2  Partials 568 568 

Impacted Files	Coverage Δ
...oud/spanner/connection/LocalConnectionChecker.java	81.57% <0.00%> (-0.48%)	⬇️
...ain/java/com/google/cloud/spanner/SessionPool.java	88.73% <0.00%> (-0.39%)	⬇️
.../com/google/cloud/spanner/AbstractReadContext.java	87.02% <0.00%> (+0.19%)	⬆️
...om/google/cloud/spanner/TransactionRunnerImpl.java	86.51% <0.00%> (+0.27%)	⬆️
...ain/java/com/google/cloud/spanner/SessionImpl.java	87.20% <0.00%> (+0.30%)	⬆️
...ogle/cloud/spanner/connection/StatementParser.java	87.50% <0.00%> (+0.33%)	⬆️
...rc/main/java/com/google/cloud/spanner/Options.java	92.85% <0.00%> (+0.59%)	⬆️
...oogle/cloud/spanner/PartitionedDmlTransaction.java	83.33% <0.00%> (+0.72%)	⬆️
...ud/spanner/SessionPoolAsyncTransactionManager.java	87.21% <0.00%> (+1.50%)	⬆️
...m/google/cloud/spanner/connection/SpannerPool.java	89.47% <0.00%> (+1.57%)	⬆️
... and 1 more

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[thiagotnunes]

It seems that the first sample spanner_set_transaction_and_request_tags does not entirely match the one we have in the client spec.

Is that true, or did we decide to change directions @larkee ?

[olavloite]

As far as I can tell, REQUEST_TAG is not yet available in (public) Cloud Spanner databases. This should therefore not be merged until the column is available.

Furthermore: The t. prefix here does not work. There's no alias t in the query below.

[mayurkale22]

It seems that the first sample spanner_set_transaction_and_request_tags does not entirely match the one we have in the client spec.

Is that true, or did we decide to change directions @larkee ?

Updated the sample wrt the client spec. PTAL

[thiagotnunes]

@mayurkale22 could you add some tests to this sample? We would like to make sure everything is working correctly before merging it.

[mayurkale22]

@mayurkale22 could you add some tests to this sample? We would like to make sure everything is working correctly before merging it.

Sure, I will add test soon. I will wait until the new column becomes visible for tests.