Add a log message when a URI template finds no expected variable

[njharter]

Problem

When configuring servers, too many times the value {keyId} is used instead of {keyID} (and/or the other way around). This causes either the services to fail or run with a bad URL endpoint.

A Bit of History

Initially keyId use to be present in commit 289f54f, but along with keyID in the same file.
Later keyID in commit 5260d89 is consistently used in both examples.

Comparison Example 1

clortho/resolver.go

Lines 28 to 31 in 289f54f

	const (
	// KeyIDParameter is the name of the URI template parameter for expanding key URIs.
	KeyIDParameterName = "keyId"
	)

clortho/resolver.go

Lines 30 to 33 in 5260d89

	const (
	// KeyIDParameter is the name of the URI template parameter for expanding key URIs.
	KeyIDParameterName = "keyID"
	)

Comparison Example 2

clortho/resolver.go

Lines 88 to 91 in 289f54f

	if err == nil {
	location, err = r.keyIDExpander.Expand(map[string]interface{}{
	KeyIDParameterName: keyID,
	})

clortho/resolver.go

Lines 199 to 202 in 5260d89

	func (r *resolver) fetchKey(ctx context.Context, keyID string, request *pendingResolverRequest) (location string, k Key, err error) {
	location, err = r.keyIDExpander.Expand(map[string]interface{}{
	KeyIDParameterName: keyID,
	})

Suggested Solution

Make this keyID value case insensitive.

[johnabass]

URI templates are governed by https://www.rfc-editor.org/rfc/rfc6570. Specifically, from section 2.3:

Variable names are case-sensitive because the name might be expanded within a case-sensitive URI component.

clortho consistently uses keyID to conform to golang naming conventions.

We could put a log message or something when no key id parameter is found.