fix(config-api): asset uplaod filePath error

**Describe the bug**
On create, config-api stores filePath as //opt/jans/jetty/jans-auth/custom/i18n (leading //). On update it re-validates the client-supplied filePath by exact string match against the config-defined /opt/... (single /) → mismatch → 500. It's a server-side path-build bug (create writes //opt, update rejects //opt); the provider just round-trips the filePath the server returned.

**Error**
`ERROR rest.resource.auth.AssetResource AssetResource.java:440-Application Error while updated asset is:Provided filePath [//opt/jans/jetty/jans-auth/custom/i18n] does not matchthe one defined in config [/opt/jans/jetty/jans-auth/custom/i18n] !`

**Expected behavior**
filePath on creation to match the config