Terraform module for storage transfer service with choice of inputs

Terraform
1

the input hcl to the module

terraform {
  source = "../path-to-my-terraform-module"
}

inputs = {
  project = dependency.project.outputs.project_id
  jobs = {
    "job_name_a" = {
      "description" = "job description A",
      "transfer_spec" = {
        "posix_data_source": {
          "root_directory": "/mnt/job"
        },
        "gcs_data_sink": {
          "bucket_name": "my-bucket"
        },
        "transfer_options": {
          "overwrite_when": "DIFFERENT",
          "delete_objects_from_source_after_transfer": true
        }
      },
      "schedule" = {
        "schedule_start_date" = {
          "year"  = 2024,
          "month" = 8,
          "day"   = 12
        },
        "repeat_interval" = "3600s"
      }
    }
  }
}

terraform module

variable "jobs" {
  description = "Map of jobs with their respective configurations"
  type        = any
}

resource "google_storage_transfer_job" "jobs" {
  for_each    = var.jobs
  project     = var.project
  description = lookup(each.value, "description", "")

  transfer_spec {
    dynamic "posix_data_source" {
      for_each = lookup(each.value.transfer_spec, "posix_data_source", [])
      content {
        root_directory = posix_data_source.value.root_directory
      }
    }

    dynamic "gcs_data_sink" {
      for_each = lookup(each.value.transfer_spec, "gcs_data_sink", [])
      content {
        bucket_name = gcs_data_sink.value.bucket_name
      }
    }

    dynamic "transfer_options" {
      for_each = lookup(each.value.transfer_spec, "transfer_options", [])
      content {
        overwrite_objects_already_existing_in_sink = lookup(transfer_options.value, "overwrite_when", "DIFFERENT") != "NEVER"
        delete_objects_from_source_after_transfer  = lookup(transfer_options.value, "delete_objects_from_source_after_transfer", false)
      }
    }
  }

  schedule {
    dynamic "schedule_start_date" {
      for_each = lookup(each.value.schedule, "schedule_start_date", [])
      content {
        year  = schedule_start_date.value.year
        month = schedule_start_date.value.month
        day   = schedule_start_date.value.day
      }
    }
    repeat_interval = lookup(each.value.schedule, "repeat_interval", "")
  }
}

output "jobs_id_list" {
  value       = [for job in google_storage_transfer_job.jobs : job.name]
  description = "List of all job names created."
}

errors are

in resource "google_storage_transfer_job" "storage_transfer":
│   15:           root_directory = posix_data_source.value.root_directory
│     ├────────────────
│     │ posix_data_source.value is "/mnt/job"
│ 
│ Can't access attributes on a primitive-typed value (string)

please let me know how can i correct this error on string?

Also like posix_data_source we can have gcs_data_source block as well. So How do we specify this choice in the terraform module and make sure that only one source is generated by the module(either posix_data_source or gcs_data_source)?