feat: update send and batch email method to also support templates

[kewynakshlley]

Summary by cubic

Add template support to send and batch email methods. You can now send emails using a published template with variables.

• New Features
  • CreateEmailOptions supports template via builder: .template(Template).
  • New Template model (id, variables) with builder; supports Map, addVariable, and varargs via Template.variable().
  • Rules: if template is set, html/text/react are not allowed; from/subject/reply_to override template defaults.
  • Tests added for send and batch with templates; utility helpers for building templates and options.

^{Written for commit 5648dbd. Summary will update automatically on new commits.}

[cubic-dev-ai]

2 issues found across 4 files

Prompt for AI agents (all 2 issues)

Understand the root cause of the following 2 issues and fix them.


<file name="src/main/java/com/resend/services/emails/model/Template.java">

<violation number="1" location="src/main/java/com/resend/services/emails/model/Template.java:25">
The Template constructor stores the builder&#39;s mutable variables map by reference, so reusing the builder mutates previously built Template instances. Make a defensive copy when assigning.</violation>
</file>

<file name="src/test/java/com/resend/services/emails/EmailsTest.java">

<violation number="1" location="src/test/java/com/resend/services/emails/EmailsTest.java:235">
Rule violated: **API Key Permission Check SDK Methods**

This new template-based send path exercises additional Resend SDK capabilities, but nothing here confirms the production API keys cover the template permissions required by the API. Please verify those credentials so template sends don’t start failing after release.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[cubic-dev-ai]

The Template constructor stores the builder's mutable variables map by reference, so reusing the builder mutates previously built Template instances. Make a defensive copy when assigning.

Prompt for AI agents

Address the following comment on src/main/java/com/resend/services/emails/model/Template.java at line 25:

<comment>The Template constructor stores the builder&#39;s mutable variables map by reference, so reusing the builder mutates previously built Template instances. Make a defensive copy when assigning.</comment>

<file context>
@@ -0,0 +1,172 @@
+     */
+    private Template(Builder builder) {
+        this.id = builder.id;
+        this.variables = builder.variables;
+    }
+
</file context>

[cubic-dev-ai]

Rule violated: API Key Permission Check SDK Methods

This new template-based send path exercises additional Resend SDK capabilities, but nothing here confirms the production API keys cover the template permissions required by the API. Please verify those credentials so template sends don’t start failing after release.

Prompt for AI agents

Address the following comment on src/test/java/com/resend/services/emails/EmailsTest.java at line 235:

<comment>This new template-based send path exercises additional Resend SDK capabilities, but nothing here confirms the production API keys cover the template permissions required by the API. Please verify those credentials so template sends don’t start failing after release.</comment>

<file context>
@@ -218,4 +218,71 @@ public void testListAttachmentsWithPagination_Success() throws ResendException {
+                .from(&quot;Acme &lt;onboarding@resend.dev&gt;&quot;)
+                .to(&quot;john.doe@example.com&quot;)
+                .subject(&quot;Welcome John!&quot;)
+                .template(template)
+                .build();
+
</file context>

[CarolinaMoraes]

💯