chore: Move import code from cds-dk to openapi

cds-plugin.js

@@ -0,0 +1,12 @@
+const cds = require('@sap/cds')
+
+const { compile, import: openapi } = require('./index')
+
+if (cds.compile?.to) cds.compile.to.openapi = compile
+
+if (cds.import?.from) cds.import.from.openapi = async function (filepath, options = {}) {
+    const src = await cds.utils.read(filepath, 'utf-8')
+    const csn = openapi.openAPI2csn(src)
+    options.inputFileKind = 'rest'
+    return csn
+}

index.js

@@ -1,5 +1,7 @@
 const { compileToOpenAPI } = require('./lib/compile');
+const importOpenAPI = require('./lib/import');
 
 module.exports = {
-    compile: compileToOpenAPI
+    compile: compileToOpenAPI,
+    import: importOpenAPI
 }