Add documentation on checked_by license parameter (#41959)

This patch adds documentation on the checked_by license direcitve
parameter that was added in #40755 but was not documented at that time.

lib/spack/docs/packaging_guide.rst

@@ -6979,3 +6979,18 @@ you probably care most about are:
 You may also care about `license exceptions
 <https://spdx.org/licenses/exceptions-index.html>`_ that use the ``WITH`` operator,
 e.g. ``Apache-2.0 WITH LLVM-exception``.
+
+Many of the licenses that are currently in the spack repositories have been
+automatically determined. While this is great for bulk adding license
+information and is most likely correct, there are sometimes edge cases that
+require manual intervention. To determine which licenses are validated and
+which are not, there is the `checked_by` parameter in the license directive:
+
+.. code-block:: python
+
+   license("<license>", when="<when>", checked_by="<github username>")
+
+When you have validated a github license, either when doing so explicitly or
+as part of packaging a new package, please set the `checked_by` parameter
+to your Github username to signal that the license has been manually
+verified.

lib/spack/spack/cmd/create.py

@@ -64,8 +64,9 @@ class {class_name}({base_class_name}):
     # maintainers("github_user1", "github_user2")
 
     # FIXME: Add the SPDX identifier of the project's license below.
-    # See https://spdx.org/licenses/ for a list.
+    # See https://spdx.org/licenses/ for a list. Upon manually verifying
-    license("UNKNOWN")
+    # the license, set checked_by to your Github username.
+    license("UNKNOWN", checked_by="github_user1")
 
 {versions}
 

lib/spack/spack/test/cmd/create.py

@@ -27,7 +27,11 @@
             [r"TestNamedPackage(Package)", r"def install(self"],
         ),
         (["file://example.tar.gz"], "example", [r"Example(Package)", r"def install(self"]),
-        (["-n", "test-license"], "test-license", [r'license("UNKNOWN")']),
+        (
+            ["-n", "test-license"],
+            "test-license",
+            [r'license("UNKNOWN", checked_by="github_user1")'],
+        ),
         # Template-specific cases
         (
             ["-t", "autoreconf", "/test-autoreconf"],