Update contribution link and clarify encrypted field configuration.

Updated README.adoc to reflect the current contribution process, replacing the outdated CLA link with the new Developer Certificate of Origin (DCO) instructions.

In mongo-encryption.adoc, updated the code sample to include the required `keyId(...)` call when configuring a field with Queryable Encryption.

Signed-off-by: Ricardo Mello <ricardohsmello@gmail.com>

Author: ricardohsmello

README.adoc

@@ -211,8 +211,9 @@ Now you are ready to build Spring Data MongoDB. Simply enter the following `mvnw
 
 If you want to build with the regular `mvn` command, you will need https://maven.apache.org/run-maven/index.html[Maven v3.8.0 or above].
 
-_Also see link:CONTRIBUTING.adoc[CONTRIBUTING.adoc] if you wish to submit pull requests, and in particular, please sign
-the https://cla.pivotal.io/sign/spring[Contributor’s Agreement] before your first non-trivial change._
+_Also see link:CONTRIBUTING.adoc[CONTRIBUTING.adoc] if you wish to submit pull requests.
+Before your first non-trivial change, please make sure your commits include a Signed-off-by line to indicate
+agreement with the https://spring.io/blog/2025/01/06/hello-dco-goodbye-cla-simplifying-contributions-to-spring#how-to-use-developer-certificate-of-origin[Developer Certificate of Origin]._
 
 === Building reference documentation
 

src/main/antora/modules/ROOT/pages/mongodb/mongo-encryption.adoc

@@ -140,10 +140,14 @@ Manual Collection Setup::
 ====
 [source,java,indent=0,subs="verbatim,quotes",role="primary"]
 ----
+BsonBinary ssnDK = clientEncryption.createDataKey("local", new com.mongodb.client.model.vault.DataKeyOptions());
+BsonBinary ageDK = clientEncryption.createDataKey("local", new com.mongodb.client.model.vault.DataKeyOptions());
+BsonBinary signDK = clientEncryption.createDataKey("local", new com.mongodb.client.model.vault.DataKeyOptions());
+
 CollectionOptions collectionOptions = CollectionOptions.encryptedCollection(options -> options
-	.queryable(encrypted(string("ssn")).algorithm("Indexed"), equality().contention(0))
-	.queryable(encrypted(int32("age")).algorithm("Range"), range().contention(8).min(0).max(150))
-	.queryable(encrypted(int64("address.sign")).algorithm("Range"), range().contention(2).min(-10L).max(10L))
+	.queryable(encrypted(string("ssn")).algorithm("Indexed").keyId(ssnDK.asUuid()), equality().contention(0))
+	.queryable(encrypted(int32("age")).algorithm("Range").keyId(ageDK.asUuid()), range().contention(8).min(0).max(150))
+	.queryable(encrypted(int64("address.sign")).algorithm("Range").keyId(signDK.asUuid()), range().contention(2).min(-10L).max(10L))
 );
 
 mongoTemplate.createCollection(Patient.class, collectionOptions); <1>