Apply configuration of SnippetsFilters to NGINX (#2604)

Problem: As a user of NGF, I want my SnippetsFilters configuration
applied to NGF's data plane, so that I can leverage NGINX features
not yet available in NGF.

Solution: Apply configuration of valid SnippetsFilters referenced in
HTTPRoutes and GRPCRoutes to the appropriate contexts in the
NGINX config. If the SnippetsFilter referenced is invalid
(wrong group or kind), the routing rule is not configured.
If the SnippetsFilter cannot be resolved, the routing rule is configured,
but the route will return a 500.

Author: kate-osborn

internal/mode/static/state/dataplane/configuration_test.go

@@ -2364,6 +2364,42 @@ func TestBuildConfiguration(t *testing.T) {
 			}),
 			msg: "SnippetsFilters with main and http snippet",
 		},
+		{
+			graph: getModifiedGraph(func(g *graph.Graph) *graph.Graph {
+				g.SnippetsFilters = map[types.NamespacedName]*graph.SnippetsFilter{
+					client.ObjectKeyFromObject(sf1.Source):             sf1,
+					client.ObjectKeyFromObject(sfNotReferenced.Source): sfNotReferenced,
+				}
+
+				return g
+			}),
+			expConf: getModifiedExpectedConfiguration(func(conf Configuration) Configuration {
+				conf.MainSnippets = []Snippet{
+					{
+						Name: createSnippetName(
+							ngfAPI.NginxContextMain,
+							client.ObjectKeyFromObject(sf1.Source),
+						),
+						Contents: "main snippet",
+					},
+				}
+				conf.BaseHTTPConfig.Snippets = []Snippet{
+					{
+						Name: createSnippetName(
+							ngfAPI.NginxContextHTTP,
+							client.ObjectKeyFromObject(sf1.Source),
+						),
+						Contents: "http snippet",
+					},
+				}
+				conf.HTTPServers = []VirtualServer{}
+				conf.SSLServers = []VirtualServer{}
+				conf.SSLKeyPairs = map[SSLKeyPairID]SSLKeyPair{}
+
+				return conf
+			}),
+			msg: "SnippetsFilters with main and http snippet",
+		},
 	}
 
 	for _, test := range tests {