Issue:
feat(redis_interface): implement functions for `HGET`, `HSET`, `HSETNX` commands

## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [x] Enhancement
- [ ] Refactoring
- [ ] Dependency updates

## Description
<!-- Describe your changes in detail -->
This PR adds wrapper functions for `HGET`, `HSET` and `HSETNX` commands under the `redis_interface` crate and updates the `router` crate to use those functions.

## Motivation and Context
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Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless its an obvious bug or documentation fix
that will have little conversation).
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This change removes the `fred` crate as a direct dependency of the `router` crate.

## How did you test it?
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
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Ran the application and created/retrieved payments via Postman.

## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable


Resolution:
<think>
PR Context:
- Title: fix(redis_interface): fix derps in `HSET` and `HSETNX` command wrappers
- Merged: 2022-12-13T12:44:19Z
- Files changed: 7 files
- Commits: 3 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates

## Description
<!-- Describe your changes in detail -->
This PR fixes some bugs introduced in #114.

The changes include:

- Rename `SetNXReply` to `SetnxReply`.
- Add `HsetnxReply` which is returned by the `HSETNX` command wrapper.
- Remove the `serialize_and_set_hash_fields()` function since it wasn't a perfect implementati
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** fix(redis_interface): fix derps in `HSET` and `HSETNX` command wrappers (#129)
Files to modify:


**crates/redis_interface/src/commands.rs**
  Remove:
    - function: pub::serialize_and_set_hash_fields

**crates/redis_interface/src/types.rs**
  Remove:
    - enum: pub::SetNXReply
  Add:
    - enum: pub::SetnxReply

**crates/router/src/db/payment_attempt.rs**
  Modify existing code

**crates/router/src/db/payment_intent.rs**
  Modify existing code

**crates/router/src/db/queue.rs**
  Modify existing code