Steeltoe: TLS private keys written to /tmp with default permissions, never deleted

Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. In Steeltoe.Configuration.Abstractions 4.0.0 through 4.1.0, when MySQL or PostgreSQL service bindings from VCAP_SERVICES include TLS client credentials, the Connectors library writes those credentials to temporary files in Path.GetTempPath() using File.CreateText. On Linux, File.CreateText creates files with mode 0644 (world-readable) under the process umask, and the files are never deleted. The same key material is protected at mode 0400 in /proc//environ. Steeltoe.Configuration.Abstractions version 4.2.0 patches the issue. If an immediate upgrade is not possible, prevent other processes from running in the container under a different UID with access to /tmp.