feat: pcu added into the go client

[bdunn313]

Add in all PCU-related endpoints to the go client

Example: Create a PCU Group

ctx := context.Background()
client, _ := astra.NewClientWithResponses("https://api.astra.datastax.com",
    astra.WithRequestEditorFn(func(ctx context.Context, req *http.Request) error {
        req.Header.Set("Authorization", "Bearer "+token)
        return nil
    }))

title := "Production PCU Group"
region := "us-east-1"
resp, _ := client.PcuCreateWithResponse(ctx, []astra.PCUGroupCreateRequest{{
    Title:         &title,
    Region:        &region,
    Reserved:      intPtr(100),
    Min:           intPtr(50),
    Max:           intPtr(200),
    InstanceType:  instanceTypePtr(astra.InstanceTypeC532xlarge),
    ProvisionType: provisionTypePtr(astra.ProvisionTypeServerless),
}})

if resp.JSON201 != nil {
    pcuGroupUUID := (*resp.JSON201)[0].Uuid
    fmt.Printf("Created PCU Group: %s\n", *pcuGroupUUID)
}

Example: Get associations and add a new one

resp, _ := client.PcuAssociationGetWithResponse(ctx, "pcu-group-uuid")

if resp.JSON200 != nil {
    for _, assoc := range *resp.JSON200 {
        fmt.Printf("Datacenter: %s, Status: %s\n",
            *assoc.DatacenterUUID, *assoc.ProvisioningStatus)
    }
}

resp, _ := client.PcuAssociationCreateWithResponse(ctx,
    "pcu-group-uuid",
    "datacenter-uuid")

if resp.StatusCode() == 201 {
    fmt.Println("Database associated with PCU group")
}