Add validation for cocoapods, cpan, and swid package types

Implements type-specific validation rules from purl-spec:

- cocoapods: Name cannot contain whitespace, plus (+) character, or
  begin with a period
- cpan: Namespace must be UPPERCASE when present (optional component)
- swid: Requires tag_id qualifier that must not be empty; GUID format
  tag_id must be lowercase

Based on official package-url type definitions:
- https://github.com/package-url/purl-spec/blob/master/types-doc/cocoapods-definition.md
- https://github.com/package-url/purl-spec/blob/master/types-doc/cpan-definition.md
- https://github.com/package-url/purl-spec/blob/master/types-doc/swid-definition.md

Author: jdalton

src/purl-type.ts

@@ -255,9 +255,38 @@ const PurlType = createHelpersNamespaceObject(
       },
     },
     validate: {
-      // TODO: cocoapods name validation
-      // TODO: cpan namespace validation
-      // TODO: swid qualifier validation
+      // https://github.com/package-url/purl-spec/blob/master/types-doc/cocoapods-definition.md
+      cocoapods(purl: PurlObject, throws: boolean) {
+        const { name } = purl
+        // Name cannot contain whitespace.
+        if (/\s/.test(name)) {
+          if (throws) {
+            throw new PurlError(
+              'cocoapods "name" component cannot contain whitespace',
+            )
+          }
+          return false
+        }
+        // Name cannot contain a plus (+) character.
+        if (name.includes('+')) {
+          if (throws) {
+            throw new PurlError(
+              'cocoapods "name" component cannot contain a plus (+) character',
+            )
+          }
+          return false
+        }
+        // Name cannot begin with a period (.).
+        if (name.charCodeAt(0) === 46 /*'.'*/) {
+          if (throws) {
+            throw new PurlError(
+              'cocoapods "name" component cannot begin with a period',
+            )
+          }
+          return false
+        }
+        return true
+      },
       // https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst#conan
       conan(purl: PurlObject, throws: boolean) {
         if (isNullishOrEmptyString(purl.namespace)) {
@@ -279,6 +308,18 @@ const PurlType = createHelpersNamespaceObject(
         }
         return true
       },
+      // https://github.com/package-url/purl-spec/blob/master/types-doc/cpan-definition.md
+      cpan(purl: PurlObject, throws: boolean) {
+        // CPAN namespace (author/publisher ID) must be uppercase when present.
+        const { namespace } = purl
+        if (namespace && namespace !== namespace.toUpperCase()) {
+          if (throws) {
+            throw new PurlError('cpan "namespace" component must be UPPERCASE')
+          }
+          return false
+        }
+        return true
+      },
       // https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst#cran
       cran(purl: PurlObject, throws: boolean) {
         return validateRequiredByType('cran', 'version', purl.version, throws)
@@ -480,6 +521,40 @@ const PurlType = createHelpersNamespaceObject(
         }
         return true
       },
+      // https://github.com/package-url/purl-spec/blob/master/types-doc/swid-definition.md
+      swid(purl: PurlObject, throws: boolean) {
+        const { qualifiers } = purl
+        // SWID requires a tag_id qualifier.
+        const tagId = qualifiers?.['tag_id']
+        if (!tagId) {
+          if (throws) {
+            throw new PurlError('swid requires a "tag_id" qualifier')
+          }
+          return false
+        }
+        // tag_id must not be empty after trimming.
+        const tagIdStr = String(tagId).trim()
+        if (tagIdStr.length === 0) {
+          if (throws) {
+            throw new PurlError('swid "tag_id" qualifier must not be empty')
+          }
+          return false
+        }
+        // If tag_id is a GUID, it must be lowercase.
+        const guidPattern =
+          /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i
+        if (guidPattern.test(tagIdStr)) {
+          if (tagIdStr !== tagIdStr.toLowerCase()) {
+            if (throws) {
+              throw new PurlError(
+                'swid "tag_id" qualifier must be lowercase when it is a GUID',
+              )
+            }
+            return false
+          }
+        }
+        return true
+      },
       // https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst#swift
       swift(purl: PurlObject, throws: boolean) {
         return (