add generic interface for transact/read transact.

[newhook]

The current db.Transact and db.ReadTransact relies on interface{} and is error prone. This PR provides a new API based around generics for Transact and ReadTransact.

It is intended to be used like:

err = fdb.Transact(db, func(t fdb.Transaction) error {
    ...
})

val, err = fdb.Transact1(db, func(t fdb.Transaction) (string, error) {
    ...
})

Any feedback, please let me know. If there is alignment on a solution, then I can add tests, and such.

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[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux CentOS 7

• Commit ID: ecf215c
• Duration 0:23:54
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
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[foundationdb-ci]

Result of foundationdb-pr-clang on Linux CentOS 7

• Commit ID: ecf215c
• Duration 0:29:57
• Result: ❌ FAILED
• Error: Error while executing command: python3 -m joshua.joshua start --tarball $(find build_output/packages -name correctness\*.tar.gz) --username ${CORRECTNESS_USERNAME} --max-runs 10000. Reason: exit status 2
• Build Log terminal output (available for 30 days)
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[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: ecf215c
• Duration 0:36:19
• Result: ❌ FAILED
• Error: Error while executing command: mvn install:install-file --batch-mode -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn -Dfile=packages/fdb-java-${FDB_VERSION}-SNAPSHOT.jar -DgroupId=org.foundationdb -DartifactId=fdb-java -Dversion=${FDB_VERSION}-SNAPSHOT -Dpackaging=jar -DgeneratePom=true. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)
• Cluster Test Logs zip file of the test logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: ecf215c
• Duration 0:39:33
• Result: ❌ FAILED
• Error: Error while executing command: python3 -m joshua.joshua start --tarball $(find build_output/packages -name correctness\*.tar.gz) --username ${CORRECTNESS_USERNAME} --max-runs 10000. Reason: exit status 2
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[johscheuer]

Thanks for the PR, could you add some test cases and examples in fdb_test.go for the new methods?

[johscheuer]

Suggested change

	* database.go
	* transact.go

[johscheuer]

Maybe a better name would be TransactWithoutReturnValue?

[johscheuer]

Could you provide some examples in which cases those different Transact1, Transact2 and Transact3 are needed?