samples: adds samples for CMEK

[thiagotnunes]

Adds samples to create an encrypted database, to create an encrypted backup and to restore to an encrypted database.

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/snippets/src/main/java/com/example/spanner/CreateBackupWithEncryptionKey.java:19, tag spanner_create_backup_with_encryption_key
• samples/snippets/src/main/java/com/example/spanner/CreateDatabaseWithEncryptionKey.java:19, tag spanner_create_database_with_encryption_key
• samples/snippets/src/main/java/com/example/spanner/RestoreBackupWithEncryptionKey.java:19, tag spanner_restore_backup_with_encryption_key

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[codecov]

Codecov Report

Merging #989 (4a7b0d5) into master (459a477) will increase coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #989      +/-   ##
============================================
+ Coverage     85.07%   85.14%   +0.06%     
- Complexity     2617     2621       +4     
============================================
  Files           154      154              
  Lines         14319    14329      +10     
  Branches       1331     1334       +3     
============================================
+ Hits          12182    12200      +18     
+ Misses         1569     1565       -4     
+ Partials        568      564       -4     

Impacted Files	Coverage Δ	Complexity Δ
...ava/com/google/cloud/spanner/v1/SpannerClient.java	86.52% <0.00%> (ø)	49.00% <0.00%> (ø%)
.../com/google/cloud/spanner/AbstractReadContext.java	86.54% <0.00%> (ø)	42.00% <0.00%> (ø%)
...om/google/cloud/spanner/TransactionRunnerImpl.java	86.07% <0.00%> (+0.14%)	10.00% <0.00%> (ø%)
...ain/java/com/google/cloud/spanner/SessionPool.java	89.12% <0.00%> (+0.19%)	73.00% <0.00%> (+1.00%)
...m/google/cloud/spanner/connection/SpannerPool.java	87.89% <0.00%> (+0.52%)	33.00% <0.00%> (ø%)
...ud/spanner/SessionPoolAsyncTransactionManager.java	87.21% <0.00%> (+1.50%)	14.00% <0.00%> (+2.00%)
.../google/cloud/spanner/SpannerExceptionFactory.java	87.96% <0.00%> (+2.77%)	48.00% <0.00%> (+2.00%)
...a/com/google/cloud/spanner/SpannerRetryHelper.java	84.61% <0.00%> (+3.66%)	3.00% <0.00%> (ø%)

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[olavloite]

More in general: This adds additional backup and restore operations to the total set of integration tests. Backup and restore operations can take a long time, so is this something that we really want?

[thiagotnunes]

@olavloite that is a good question. I think that it is important to have these sample tests even if the backup / restore operations take a long time. However, I think we should move the samples tests to be executed in the nightly build only. This way we do not impact the day to day operation.

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