load balancers: introduce new type field

[asaha2]

Introduce new load balancer Type field to allow specifying the type of load balancer to be created:

• REGIONAL: supports target droplets within the same region/vpc
• GLOBAL: supports target droplets across multiple regions/vpcs

Omitting the Type field in the Create request implies REGIONAL by default.

[bentranter]

For the new Type field, it looks like it can either be REGIONAL or GLOBAL.

Could you include these as constants? Something like,

const (
    LoadBalancerTypeGlobal = "GLOBAL"
    LoadBalancerTypeRegional = "REGIONAL"
)

[asaha2]

For the new Type field, it looks like it can either be REGIONAL or GLOBAL.

Could you include these as constants? Something like,

const (
    LoadBalancerTypeGlobal = "GLOBAL"
    LoadBalancerTypeRegional = "REGIONAL"
)

We allow case insensitive type parameter: hence all of REGIONAL, regional or reGIOnAL would be accepted.

[bentranter]

@asaha2 It would still make it easier for users to discover and to pass one the correct load balancer types if we can provide some kind of constant – it doesn't necessarily have to be uppercase.

[bentranter]

LGTM! Thanks @asaha2. If you want you can merge now, or if you want you can wait for @bbassingthwaite to give it a review.