refactor(scanners): Rename a snippet's license to singular

While the expression could contain compound sub-expressions, it is still
a single expression. This aligns with `LicenseFinding` and also helps to
distinguish from a list of expressions in an upcoming change.

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

model/src/main/kotlin/Snippet.kt

@@ -47,9 +47,9 @@ data class Snippet(
     val purl: String,
 
     /**
-     * The license of the component the code snippet is commit from.
+     * The SPDX license expression of the component the code snippet is coming from.
      */
-    val licenses: SpdxExpression,
+    val license: SpdxExpression,
 
     /**
      * A map for scanner-specific snippet data that cannot be mapped into any generalized property, but still needs to

plugins/reporters/freemarker/src/main/kotlin/FreemarkerTemplateProcessor.kt

@@ -348,7 +348,7 @@ class FreemarkerTemplateProcessor(
          */
         @Suppress("UNUSED") // This function is used in the templates.
         fun collectLicenses(snippetsFindings: Collection<SnippetFinding>): Set<String> =
-            snippetsFindings.flatMap { findings -> findings.snippets }.map { snippet -> snippet.licenses.toString() }
+            snippetsFindings.flatMap { findings -> findings.snippets }.map { snippet -> snippet.license.toString() }
                 .toSet()
 
         /**

plugins/scanners/fossid/src/main/kotlin/FossIdScanResults.kt

@@ -373,10 +373,10 @@ private fun getLicenseFindingFromSnippetChoice(
     return if (isSnippetChoice) {
         logger.info {
             "Adding snippet choice for ${sourceLocation.prettyPrint()} " +
-                "with license ${snippet.licenses} to the license findings."
+                "with license ${snippet.license} to the license findings."
         }
 
-        LicenseFinding(snippet.licenses, sourceLocation)
+        LicenseFinding(snippet.license, sourceLocation)
     } else {
         null
     }

plugins/scanners/fossid/src/test/kotlin/FossIdLicenseMappingTest.kt

@@ -74,7 +74,7 @@ class FossIdLicenseMappingTest : WordSpec({
             findings should haveSize(1)
             findings.first() shouldNotBeNull {
                 snippets.first() shouldNotBeNull {
-                    licenses.toString() shouldBe "Apache-2.0"
+                    license.toString() shouldBe "Apache-2.0"
                 }
             }
         }
@@ -96,7 +96,7 @@ class FossIdLicenseMappingTest : WordSpec({
             findings should haveSize(1)
             findings.first() shouldNotBeNull {
                 snippets.first() shouldNotBeNull {
-                    licenses.toString() shouldBe "GFDL-1.2-only"
+                    license.toString() shouldBe "GFDL-1.2-only"
                 }
             }
         }
@@ -118,7 +118,7 @@ class FossIdLicenseMappingTest : WordSpec({
             findings should haveSize(1)
             findings.first() shouldNotBeNull {
                 snippets.first() shouldNotBeNull {
-                    licenses.toString() shouldBe "Apache-2.0"
+                    license.toString() shouldBe "Apache-2.0"
                 }
             }
         }
@@ -146,7 +146,7 @@ class FossIdLicenseMappingTest : WordSpec({
             findings should haveSize(1)
             findings.first() shouldNotBeNull {
                 snippets.first() shouldNotBeNull {
-                    licenses shouldBe SpdxConstants.NOASSERTION.toSpdx()
+                    license shouldBe SpdxConstants.NOASSERTION.toSpdx()
                 }
             }
         }