Incorrect parent can result in 500

[donaldgray]

#272 updated requirements for parent to be a fully qualified URL. I accidentally encountered a bug where I submitted a parent using localhost URL, rather than expected development environment URL.

e.g. https://localhost:7230/7/collections/root rather than https://presentation-api.dlcs.digirati.io//7/collections/root

This resulted in a 500 exception, rather than a 400. From logs:

[16:11:25 DBG API.Features.Manifest.ManifestWriteService b8023e41-1ac1-44d6-b51c-f89cf55191b7] Manifest staging_test for Customer 7 doesn't exist, creating
[16:11:25 ERR API.Features.Manifest.ManifestWriteService b8023e41-1ac1-44d6-b51c-f89cf55191b7] Error upserting manifest staging_test for customer 7
System.ArgumentOutOfRangeException: startIndex cannot be larger than length of string. (Parameter 'startIndex')
at System.String.ThrowSubstringArgumentOutOfRange(Int32 startIndex, Int32 length)
at System.String.Substring(Int32 startIndex)
at Repository.Paths.PathParser.GetHierarchicalFullPathFromPath(String presentationParent, Int32 customerId, String baseUrl) in /src/Repository/Paths/PathParser.cs:line 62
at API.Helpers.ParentSlugParser.RetrieveParentFromPresentation(IPresentation presentation, Int32 customerId, CancellationToken cancellationToken) in /src/API/Helpers/ParentSlugParser.cs:line 163
at API.Helpers.ParentSlugParser.TryGetParentFromPresentation[T](IPresentation presentation, Int32 customerId, CancellationToken cancellationToken) in /src/API/Helpers/ParentSlugParser.cs:line 127
at API.Helpers.ParentSlugParser.TryGetParent[T](IPresentation presentation, Int32 customerId, CancellationToken cancellationToken)
at API.Helpers.ParentSlugParser.Parse[T](T presentation, Int32 customerId, String id, CancellationToken cancellationToken)
at API.Features.Manifest.ManifestWriteService.CreateInternal(WriteManifestRequest request, String manifestId, CancellationToken cancellationToken) in /src/API/Features/Manifest/ManifestWriteService.cs:line 152
at API.Features.Manifest.ManifestWriteService.Upsert(UpsertManifestRequest request, CancellationToken cancellationToken) in /src/API/Features/Manifest/ManifestWriteService.cs:line 110