github: add dedicated model for create PR body

this refactoring replaces `NewPullRequestData` that was serialized into
Json and used as a payload for POST /repos/{owner}/{repo}/pulls
(creating PR on GitHub) because `NewPullRequestData` contains fields
that are not processed by GitHub API (such as labels, assignees,
reviewers). New model only has fields that are expected by GitHub API.

Author: danielleontiev

modules/core/src/main/scala/org/scalasteward/core/forge/data/NewPullRequestData.scala

@@ -17,8 +17,6 @@
 package org.scalasteward.core.forge.data
 
 import cats.syntax.all._
-import io.circe.Encoder
-import io.circe.generic.semiauto._
 import org.http4s.Uri
 import org.scalasteward.core.data._
 import org.scalasteward.core.edit.EditAttempt
@@ -43,9 +41,6 @@ final case class NewPullRequestData(
 )
 
 object NewPullRequestData {
-  implicit val newPullRequestDataEncoder: Encoder[NewPullRequestData] =
-    deriveEncoder
-
   def bodyFor(
       update: Update,
       edits: List[EditAttempt],

modules/core/src/main/scala/org/scalasteward/core/forge/github/GitHubApiAlg.scala

@@ -46,8 +46,9 @@ final class GitHubApiAlg[F[_]](
 
   /** https://developer.github.com/v3/pulls/#create-a-pull-request */
   override def createPullRequest(repo: Repo, data: NewPullRequestData): F[PullRequestOut] = {
+    val payload = PullRequestPayload.from(data)
     val create = client
-      .postWithBody[PullRequestOut, NewPullRequestData](url.pulls(repo), data, modify(repo))
+      .postWithBody[PullRequestOut, PullRequestPayload](url.pulls(repo), payload, modify(repo))
       .adaptErr(SecondaryRateLimitExceeded.fromThrowable)
 
     for {

modules/core/src/main/scala/org/scalasteward/core/forge/github/PullRequestPayload.scala

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2018-2023 Scala Steward contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.scalasteward.core.forge.github
+
+import io.circe.Encoder
+import io.circe.generic.semiauto.deriveEncoder
+import org.scalasteward.core.forge.data.NewPullRequestData
+import org.scalasteward.core.git.Branch
+
+final case class PullRequestPayload(
+    title: String,
+    body: String,
+    head: String,
+    base: Branch,
+    draft: Boolean
+)
+object PullRequestPayload {
+  implicit val encoder: Encoder[PullRequestPayload] = deriveEncoder
+
+  def from(newPullRequestData: NewPullRequestData): PullRequestPayload =
+    PullRequestPayload(
+      title = newPullRequestData.title,
+      body = newPullRequestData.body,
+      head = newPullRequestData.head,
+      base = newPullRequestData.base,
+      draft = newPullRequestData.draft
+    )
+}