feat: Begins live database client tests.

Sources/ProjectClient/ProjectClientError.swift

@@ -0,0 +1,35 @@
+import Foundation
+import ManualDCore
+
+public struct ProjectClientError: Error {
+  public let reason: String
+
+  public init(_ reason: String) {
+    self.reason = reason
+  }
+
+  static func notFound(_ notFound: NotFound) -> Self {
+    .init(notFound.reason)
+  }
+
+  enum NotFound {
+    case project(Project.ID)
+    case frictionRate(Project.ID)
+
+    var reason: String {
+      switch self {
+      case .project(let id):
+        return "Project not found. id: \(id)"
+      case .frictionRate(let id):
+        return """
+          Friction unable to be calculated. id: \(id)
+
+          This usually means that not all the required steps have been completed.
+
+          Calculating the friction rate requires the component pressure losses to be set and
+          have a max equivalent length for both the supply and return.
+          """
+      }
+    }
+  }
+}