feat: Add an SPDX license text provider

Add a license text provider for SPDX licenses. The provider uses the
license texts from the resources of the `:utils:spdx-utils` module.

Signed-off-by: Martin Nonnenmacher <martin.nonnenmacher@bosch.com>

Author: mnonnenmacher

plugins/license-fact-providers/spdx/build.gradle.kts

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2025 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+plugins {
+    // Apply precompiled plugins.
+    id("ort-plugin-conventions")
+}
+
+dependencies {
+    api(projects.plugins.licenseFactProviders.licenseFactProviderApi)
+
+    implementation(projects.utils.spdxUtils)
+
+    ksp(projects.plugins.licenseFactProviders.licenseFactProviderApi)
+}

plugins/license-fact-providers/spdx/src/main/kotlin/SpdxLicenseFactProvider.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2025 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.plugins.licensefactproviders.spdx
+
+import org.ossreviewtoolkit.plugins.api.OrtPlugin
+import org.ossreviewtoolkit.plugins.api.PluginDescriptor
+import org.ossreviewtoolkit.plugins.licensefactproviders.api.LicenseFactProvider
+import org.ossreviewtoolkit.plugins.licensefactproviders.api.LicenseFactProviderFactory
+
+@OrtPlugin(
+    id = "SPDX",
+    displayName = "SPDX License Fact Provider",
+    description = "A provider for SPDX license facts.",
+    factory = LicenseFactProviderFactory::class
+)
+class SpdxLicenseFactProvider(
+    override val descriptor: PluginDescriptor = SpdxLicenseFactProviderFactory.descriptor
+) : LicenseFactProvider {
+    override fun getLicenseText(licenseId: String) = getLicenseTextResource(licenseId)?.readText()
+
+    override fun hasLicenseText(licenseId: String) = getLicenseTextResource(licenseId) != null
+
+    private fun getLicenseTextResource(licenseId: String) = object {}.javaClass.getResource("/licenses/$licenseId")
+}

plugins/license-fact-providers/spdx/src/test/kotlin/SpdxLicenseFactProviderTest.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2025 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.plugins.licensefactproviders.spdx
+
+import io.kotest.core.spec.style.WordSpec
+import io.kotest.inspectors.forAll
+import io.kotest.matchers.should
+import io.kotest.matchers.shouldBe
+import io.kotest.matchers.shouldNot
+import io.kotest.matchers.string.beEmpty
+import io.kotest.matchers.string.contain
+import io.kotest.matchers.string.haveLength
+
+import org.ossreviewtoolkit.utils.spdx.SpdxLicense
+
+class SpdxLicenseFactProviderTest : WordSpec({
+    val provider = SpdxLicenseFactProvider()
+
+    "getLicenseText()" should {
+        "return the license text for Apache-2.0" {
+            val text  = provider.getLicenseText(SpdxLicense.APACHE_2_0.id)
+            text should contain("Apache License")
+            text should haveLength(11357)
+        }
+
+        "return the license text for all SPDX licenses" {
+            enumValues<SpdxLicense>().forAll { license ->
+                provider.getLicenseText(license.id) shouldNot beEmpty()
+            }
+        }
+
+        "return null for an unknown license" {
+            provider.getLicenseText("UnknownLicense") shouldBe null
+        }
+    }
+
+    "hasLicenseText()" should {
+        "return true for all SPDX licenses" {
+            enumValues<SpdxLicense>().forAll {
+                provider.hasLicenseText(it.id) shouldBe true
+            }
+        }
+
+        "return false for an unknown license" {
+            provider.hasLicenseText("UnknownLicense") shouldBe false
+        }
+    }
+})