Extend permission predicates to check requests content

[ujibang]

Brief overview

mongoAclAuthorizer and fileAclAuthorizer use predicates to define permissions.

Add new predicates to check the request content.

Rationale

In many cases it would be very useful to define a permission on the basis of the request content.

Detailed documentation

predicate
bson-request-prop-equals	true if the request content is bson and the value of the property key (can use the dot notation) is equal to value	if the request content is {"sub": { "foo": "bar" }} then bson-request-prop-equals(key=sub.foo, value='"bar"') and bson-request-prop-equals(key=sub, value='{"foo": "bar"}') is true; bson-request-prop-equals(key=sub.foo, value='"baz"') is false
bson-request-array-contains	true if the request content is bson and the property key (can use the dot notation) is an array that contains all values	if the request content is { "a": [ "foo", "bar" ] } then bson-request-array-contains(key=a, values='"foo"' ) and bson-request-array-contains(key=a, values={ '"foo"', '"bar"' } ) aretrue; bson-request-array-contains(key=a, values={ '"foo"', '"baz"' } ) is false
bson-request-array-is-subset	true if the request content is bson and the property 'key' (can use the dot notation) is an array that is a subset of 'values'	if the request content is { "a": [ "foo", "bar" ] } then bson-request-array-is-subset(key=a, values={ '"foo"', '"bar"', '"baz"' }) is true; bson-request-array-is-subset(key=a, values={ '"foo"', '"baz"' }) is false

Note: the double quotes in values since each element must be valid bson such as 1 (number), "1" (string), "bar" (string) or {"foo": "bar"} (object)

[ujibang]

documented in https://restheart.org/docs/security/authorization#predicates