fix(pg-instrumentation): capture query props when passed as class instance

[GochoMugo]

Which problem is this PR solving?

When using sql-templating libraries such as sql-template-strings, the query object is usually not a plain object, and instead a class instance.

An extracted snippet:

class SQLStatement {
  constructor(strings, values) {
    this.strings = strings
    this.values = values
  }

  /** Returns the SQL Statement for node-postgres */
  get text() {
    return this.strings.reduce((prev, curr, i) => prev + '$' + i + curr)
  }

  setName(name) {
    this.name = name
    return this
  }
}

function SQL(strings) {
  return new SQLStatement(strings.slice(0), Array.from(arguments).slice(1))
}

This class would be instantiated, for example, when using template string:

client.query(SQL`select ...`);

With the changes added in PR #3196, the text property from the Statement class above would not be captured when using the spread operator i.e. { ...arg0 }.

For example,

class Klass {
  constructor() {
    this.foo = 1;
  }
  get bar() {
    return 2;
  }
}
const instance = new Klass();
const obj = { ...instance };

assert(obj.foo === 1);
assert(obj.bar === undefined); // `bar` is not set!

Short description of the changes

The current fix is to explicitly capture name and text props while still using the spread operator.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: GochoMugo / name: Gocho Mugo (36f605d, b8524b1)

[maryliag]

instead of updating this test, can you add a new one, this way we can check changes work with both scenarios?

[GochoMugo]

@maryliag Addressed in commit b8524b1.