Composable filters as request params

[unnawut]

Closes #334

Overview

This PR adds support for a more advanced filtering. Instead of just search_term and search_terms, it's able to filter by conditions like eq (equals), neq (not equals), lt (less than), gte (greater than), etc.

Changes

• Add a new EWallet.Web.MatchAllParser to support filtering with all conditions
• Add a new EWallet.Web.MatchAnyParser to support filtering with any conditions

Implementation Details

This PR took inspirations from various existing open-sourced libraries but decided to write from scratch as the libraries are either very feature-rich that we use a very small subset of the feature, or very simple that it could easily be built on our existing parsers.

Also note that "match_any" is limited to 5 unique associations. This is due to the fact that Ecto supports only positional reference on joins. Named joins is coming in Ecto 3.0 but the release date is not set. So, I did a workaround by mapping the join sequence and build the dynamic query by having a fixed number of bindings (fixed to 5).

Usage

Supported comparators: eq, neq, lt, lte, gt, gte, contains and starts_with.

For example, the attributes below will filter for confirmed transactions that came from or went to the user with username "alice".

POST /transaction.all
{
  "match_all": [
    {
      "field": "status",
      "comparator": "eq",
      "value": "confirmed"
    }
  ],
  "match_any": [
    {
      "field": "from_user.username",
      "comparator": "eq",
      "value": "alice"
    },
    {
      "field": "to_user.username",
      "comparator": "eq",
      "value": "alice"
    }
  ]
}

Impact

New optional attributes: match_all and match_any added to /transaction.all's request format. No DB changes.

[unnawut]

Remaining:

• Support field value type casting similar to {field, :uuid} in the existing SearchParser
• Support nested field (e.g. filter transactions by from_account.name, etc.)
• Support predicate e.g. match: all or match: any

[unnawut]

Example for multiple predicates:

POST /transaction.all
{
  "match_all": [
    {
      "field": "from_user.id",
      "comparator": "eq",
      "value": "alice_id"
    },
    {
      "field": "to_user.id",
      "comparator": "eq",
      "value": "bob_id"
    }
  ],
  "match_any": [
    {
      "field": "status",
      "comparator": "eq",
      "value": "confirmed"
    },
    {
      "field": "status",
      "comparator": "eq",
      "value": "approved"
    }
  ]
}

---

Edited: removed "filters" level

[unnawut]

@T-Dnzt Added starts_with, OpenAPI specs and markdown docs. Please review again.