Add Release Api

[eutkin]

https://docs.gitlab.com/ee/api/tags.html#create-a-new-release
https://docs.gitlab.com/ee/api/tags.html#update-a-release

[gmessner]

@eutkin
Thank you for the contribution. Looks good, just a few small changes are requested.

[gmessner]

It is good practice to not use wildcard imports, please change this to only import the types being used.

[gmessner]

It is good practice to not use wildcard imports, please change this to only import the types being used.

[gmessner]

It is good practice to not use wildcard imports, please change this to only import the types being used.

[gmessner]

It is good practice to not use wildcard imports, please change this to only import the types being used.

[gmessner]

All enums should be uppercase, and to make the enum work correctly with this library this enum should look like this:

public enum RefType {

    BRANCH, TAG, ALL;

    private static JacksonJsonEnumHelper<RefType> enumHelper = new JacksonJsonEnumHelper<>(RefType.class);

    @JsonCreator
    public static RefType forValue(String value) {
        return enumHelper.forValue(value);
    }

    @JsonValue
    public String toValue() {
        return (enumHelper.toString(this));
    }

    @Override
    public String toString() {
        return (enumHelper.toString(this));
    }
}

[eutkin]

ok, i done, thank you

[gmessner]

Changes look good, thanks for making them.

[gmessner]

@eutkin
This has been released in 4.8.28

[gmessner]

@eutkin Just a heads up.

The createRelease() and updateRelease() methods along with all the tag related methods have been moved to a new API called TagsApi. This was done as this library tries to maintain a one-to-one relationship with the GitLab API docs, and these methods are all in the Tags API at:
https://docs.gitlab.com/ce/api/tags.html

Thanks again for your contribution.