Add GraphQL fields to `PullRequests` query

[danbi2990]

1. Update PullRequests query as follows:

PullRequests Query

query PullRequests(
  $owner: String!
  $name: String!
  $first: Int
  $last: Int
  $before: String
  $after: String
) {
  repository(owner: $owner, name: $name) {
    pullRequests(first: $first, last: $last, before: $before, after: $after) {
      pageInfo {
        hasNextPage
        endCursor
      }
      nodes {
        id
        number
        title
        body
        state
        createdAt
        updatedAt
        closedAt
        mergedAt
        author {
          __typename
          ... on User {
            login
          }
        }
        additions
        deletions
        url
        repository {
          owner {
            __typename
            login
          }
          name
        }
        labels(last: 5) {
          nodes {
            name
          }
        }
        comments(last: 100) {
          totalCount
          nodes {
            body
            createdAt
            updatedAt
            author {
              __typename
              ... on User {
                login
              }
            }
          }
        }
        reviewDecision
        assignees(last: 15) {
          nodes {
            login
          }
        }
        reviewRequests(last: 10) {
          nodes {
            requestedReviewer {
              __typename
              ... on User {
                login
              }
            }
          }
        }
        reviews(last: 10) {
          totalCount
          nodes {
            author {
              __typename
              ... on User {
                login
              }
            }
            state
            body
            url
            createdAt
            publishedAt
            submittedAt
            isMinimized
            comments(last: 100) {
              totalCount
              nodes {
                body
                createdAt
                updatedAt
                author {
                  __typename
                  ... on User {
                    login
                  }
                }
              }
            }
          }
        }
        commits(last: 20) {
          totalCount
          nodes {
            commit {
              additions
              deletions
              message
              messageBody
              author {
                user {
                  login
                }
              }
              changedFilesIfAvailable
              committedDate
              committer {
                user {
                  login
                }
              }
            }
          }
        }
      }
    }
  }
}

This version includes the fields identified in the relevant Notion document. Additional fields may be added later as needed.

2. Add fields to graphql::pull_request::PullRequest struct

To store the retrieved data in the database, the graphql::pull_request::PullRequest struct must be updated. Each field returned by the GraphQL query should be mapped to a corresponding field in the struct.