add to postgresql_type.go omitempty annotation

[Thunderbolt32]

I use the PostgreSQL type to configure a struct instance in golang to create the resource in the k8s cluster.

To create the https://github.com/zalando/postgres-operator/blob/master/manifests/minimal-postgres-manifest.yaml in golang it is necessary to add some more omitempty annotations to unset values.

Closes #1221

[FxKu]

Looks similar to #1022
Can you check if there are more sections, that require omitempty?

[Thunderbolt32]

In fact it is similar to #1022. As I was still working with v.1.5.0, I had a lot more bugs until I switched to the current master branch.

@FxKu Yes, I'll look at it again. It seems that more pointers would also be useful, because no structure values can be set on maps in Golang. However, I do not know if this would break compatibility. However, I will change it first.

[Thunderbolt32]

One thing that would most likely require a code change would be to solve the "not addressable" problem by using struct Pointers (instead of structs) https://stackoverflow.com/a/32751792

However, it only seems to be seriously needed in one case

type PostgresSpec struct {
        ...
	PreparedDatabases     map[string]PreparedDatabase `json:"preparedDatabases,omitempty"`
        ...
}

type PreparedDatabase struct {
	PreparedSchemas map[string]PreparedSchema `json:"schemas,omitempty"`
	...
}

[FxKu]

using pointers for the PreparedDatabase structs sound like a story for another PR. I'm also not sure how easy it is to make this backwards compatible.

[Thunderbolt32]

I have removed the default value and resolved your review.

[Thunderbolt32]

Is the E2E test Flaky? I do not quite understand why the test should fail after this change.

[FxKu]

👍

[Jan-M]

👍