Expose access url in database branch struct

This ensures we have access in dependencies to the host URL and we can
use that instead of trying to construct something manually.

Also removes the dbutil package which isn't used anywhere and would need
big refactors for the new access url pattern. It's easier to remove it.

Author: dbussink

Diff for: planetscale/branches.go

@@ -11,13 +11,14 @@ import (
 
 // DatabaseBranch represents a database branch.
 type DatabaseBranch struct {
-	Name         string    `json:"name"`
-	ParentBranch string    `json:"parent_branch"`
-	Region       Region    `json:"region"`
-	Production   bool      `json:"production"`
-	CreatedAt    time.Time `json:"created_at"`
-	UpdatedAt    time.Time `json:"updated_at"`
-	Status       string    `json:"status,omitempty"`
+	Name          string    `json:"name"`
+	ParentBranch  string    `json:"parent_branch"`
+	Region        Region    `json:"region"`
+	Production    bool      `json:"production"`
+	CreatedAt     time.Time `json:"created_at"`
+	UpdatedAt     time.Time `json:"updated_at"`
+	AccessHostURL string    `json:"access_host_url"`
+	Status        string    `json:"status,omitempty"`
 }
 
 type databaseBranchesResponse struct {