CreamAsset fails save() when given a Specific ID or propName.

Thank you for the wonderful library.

For example, initializing CreamAsset causes save() inside init() to fail.

CreamAsset.create(object: SomeObject, propName: "https://example.com/", data: someData)

CreamAsset generates uniqueFileName as the concatenation of Object's ID and propName:.

https://github.com/caiyue1993/IceCream/blob/1d6cc98831a743864176e0cc9dbddf8d0ad2e0cc/IceCream/Classes/CreamAsset.swift#L30

Next, CreamAsset.filePath use URL.appendingPathComponent() to generate a filePath from the uniqueFileName generated in the previous section, as shown below.

https://github.com/caiyue1993/IceCream/blob/1d6cc98831a743864176e0cc9dbddf8d0ad2e0cc/IceCream/Classes/CreamAsset.swift#L47

The URL contains the directory separator '/'. Therefore, the generated CreamAsset points to a file in a directory that does not exist in the generated filePath. Therefore, save() called in init() will fail.

https://github.com/caiyue1993/IceCream/blob/1d6cc98831a743864176e0cc9dbddf8d0ad2e0cc/IceCream/Classes/CreamAsset.swift#L31

I can't suggest a solution "correct" because I don't know the set of characters that can't be used as filenames, but as far as I'm concerned, I can work around this problem by making init() generate uniqueFileName like this:.

self.uniqueFileName = "\(objectID)_\(propName)".addingPercentEncoding(withAllowedCharacters: CharacterSet(charactersIn: "/").inverted) ?? "\(objectID)_\(propName)"

Of course, if I don't use "/" for the Object ID or propName, I shouldn't have any problems. However, in my project, URL is used for ID of Object, so I think it is difficult to avoid this problem. If possible, I would appreciate it if IceCream could take care of it. Thank you in advance.

Expected behavior

let asset = CreamAsset.create(object: SomeObject, propName: "https://example.com/", data: someData)

asset.storedData() is not return nil