Load multiple certificates from a single trust root file

[josephnoir]

Motivation

When passing a PEM file with multiple certificates as trust roots, only the first one is loaded.

Modifications

Instead of creating a NIOSSLCertificate directly, use a function that loads multiple certificates from a PEM file. Add a test case that creates a certificate chain in a temporary directory to verify the expected behavior.

Result

Multiple certificates can be loaded from a single PEM file.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: josephnoir / name: Raphael (dfc6fba, 67d2130, c359917, 3dd21e8, 3a4650d, 4943d52, 7007625, 4d2dc3b, 7a4dd68)

[glbrntt]

We should probably use fromPEMBytes here as well

[glbrntt]

Do we need the indirection here? Can we just switch over serializationFormat.wrapped?

[glbrntt]

Can you add Path to the end of each of these?

[glbrntt]

Same here, can you add Path to the end of each of these?

[glbrntt]

Rather than a dictionary can we just have a struct with a property for each of these? We can avoid the ! when accessing them each time then.

[glbrntt]

This matters much less because it's in tests, but it's worth mentioning anyway. In structs, let is very rarely the right choice (vs var). In this instance it should really be a static so that it's not stored inline in the struct.

In general though, if this was passed in by the caller in the init then it should still be a var, because there's nothing stopping the caller from creating a new instance with a different value:

struct CertificateChain {
  let serverName: String
  init(serverName: String) { self.serverName = serverName }
}

let chain = CertificateChain(serverName: "foo")
chain.serverName = "bar" // not allowed; chain isn't mutable

var chain2 = chain
chain2.serverName = "bar" // Agh, not allowed!
chain2 = CertificateChain(serverName: "bar") // allowed, but annoying

If it were a var:

struct CertificateChain {
  var serverName: String
  init(serverName: String) { self.serverName = serverName }
}

let chain = CertificateChain(serverName: "foo")
chain.serverName = "bar" // not allowed; chain isn't mutable

var chain2 = chain
chain2.serverName = "bar" // allowed, great!

[glbrntt]

If you put #function it will default to the calling function.

Suggested change

	public func writeToTemp(fileTag: String) throws -> [Files: String] {
	public func writeToTemp(fileTag: String = #function) throws -> [Files: String] {

[glbrntt]

Let's just use a nominal type here

[glbrntt]

LGTM, thank you!