v1.0.0 Release (GA)

Breaking Changes

• feat!: add support for QueryOptions (#1351), this is a breaking
  change for any developers that used
  Connection::SqlParams::placeholder_do_not_use_name_will_change.
• feat!: implement SessionPool session refresh (#1425), this is a
  breaking change as the return type for
  SessionOptions::keep_alive_interval changed from
  std::chrono::minutes to std::chrono::seconds.

We believe the risk of developers being impacted by these changes
is small, but do apologize if this impacts you.

Other Changes

• feat: add Managed Backup feature (#1358)
• feat: sessions are automatically created and refreshed by
  background threads as described in:
  https://cloud.google.com/spanner/docs/sessions#best_practices
• We made multiple improvements (detailed below) to the documentation and
  code samples.
• fix: polling policy stops after 'too many' successes (#1427)
• feat: clean up main doxygen page (#1404)
• feat: implement async session creation (#1405)
• fix: avoid deadlocks during shutdown (#1397)
• feat: streaming Value STRING only quotes in aggregates (#1401)
• doc: small improvements to Client samples (#1398)
• doc: link existing example for ExecuteBatchDml (#1395)
• doc: update snippets for all mutation types (#1394)
• fix: Value::op==() correctly handles Date and Timestamp (#1386)
• feat: taught Date how to stream itself (#1385)
• feat: escape non-printable bytes in Value::op<< (#1371)
• docs: add snippets for Commit() with a mutator or mutations (#1374)
• docs: updated snippets and samples for profile and analyze methods (#1364)
• feat: Value streaming respects io manipulators (#1362)
• feat: SqlStatement uses op<<(Value) (#1361)
• cleanup: make use of the new Client::Commit(Mutations) overload (#1359)
• feat: add ostream operator for Value (#1336)
• feat: refactor and enhance session creation logic (#1343)
• doc: link to the style guide in the common repo (#1348)
• fix: associate each Session with a Channel (#1346)
• feat: moved INSTALL.md -> doc/packaging.md (#1341)
• fix: use correct quickstart URL (#1339)
• feat: simplify README.md (#1338)
• doc: add more snippets to documentation (#1331)
• doc: an example of spanner::GetSingularRow (#1327)