[E-create < E-ivan] Add create docs

mage/query-modules/cpp/create.md

@@ -103,7 +103,6 @@ CALL create.nodes(["Human", "Soldier"], [{branch: "Marines", MOS: "Gunner"}, {br
 +---------------------------------------------------------------------------------------------------------------------+
 ```
 
-
 ### `set_property(nodes, key, value)`
 
 Sets the property of the input node(s), based on the provided key-value pair. If the property doesn't exist, creates a new one. Input node(s) can be a single node, node ID, or a list of nodes and node IDs. Otherwise, an exception is thrown.
@@ -298,3 +297,128 @@ MATCH (p:Person) CALL create.remove_labels(p, ["Student", "Engineer"]) YIELD nod
 | }                          |
 +----------------------------+
 ```
+
+### `relationship(from, relationshipType, properties, to)`
+
+Creates a new relationship with the given type and properties directed from->to.
+
+#### Input:
+
+- `from: Node` ➡ tail node
+- `relationshipType: string` ➡ relationship type
+- `properties: Map` ➡ properties of the new relationship(s)
+- `to: Node` ➡ head node
+
+#### Output:
+
+- `relationship: Relationship` ➡ the new relationship(s)
+
+#### Usage:
+
+```cypher
+CREATE (p:Person {name: "Cillian Murphy"});
+CREATE (m:Movie {title:"Oppenheimer"});
+
+MATCH (p:Person {name: "Cillian Murphy"}) MATCH (m:Movie {title: "Oppenheimer"}) CALL create.relationship(p, "ACTED_IN", {roles:['Oppenheimer']}, m) YIELD relationship RETURN relationship;
+```
+
+```plaintext
++-----------------------------+
+| relationship                |
++-----------------------------+
+| {                           |
+|     "id": 0,                |
+|     "start": 0              |
+|     "end": 0                |
+|     "label": "Acted_in"     |
+|     "properties": {         |
+|       roles: ["Oppenhimer"] |
+|     },                      |
+|     "type": "relationship"  |
+| }                           |
++-----------------------------+
+```
+
+### `set_rel_properties(relationships, keys, values)`
+
+Adds the provided properties to the given relationships and returns the modified relationships. If the property already exists it is modified.
+
+#### Input:
+
+- `relationships: int|Relationship|List[int|Relationship]` ➡ relationships to be modified given by their object or id
+- `keys: List[string]` ➡ list of all the property keys to be added to the relationship(s)
+- `values: List[Any]` ➡ list of all the corresponding property values to be added to the relationship(s)
+
+#### Output:
+
+- `relationship: Relationship` ➡ the modified relationship(s)
+
+#### Usage:
+
+```cypher
+CREATE (idora:Person {name: "Idora"})
+CREATE (ivan:Person {name: "Ivan"})
+CREATE (ivan)-[:Friend {since:"long ago"}]->(idora);
+
+MATCH (:Person)-[friends:Friend]->(:Person) CALL create.set_rel_properties(friends, ["really", "until"], [true, "forever"]) YIELD relationship RETURN relationship
+```
+
+```plaintext
++----------------------------+
+| relationship               |
++----------------------------+
+| {                          |
+|     "id": 0,               |
+|     "start": 1,            |
+|     "end": 0,              |
+|     "label": "Friend",     |
+|     "properties": {        |
+|       "really": true,      |
+|       "since": "long ago", |
+|       "until": "forever"  |
+|     },                     |
+|     "type": "relationship" |
+| }                          |
++----------------------------+
+```
+
+### `remove_rel_properties(relationships, keys)`
+
+Removes the provided properties from the given relationships and returns the modified relationships. If a property doesn't exist in the given relationship nothing happens with it.
+
+#### Input:
+
+- `relationships: int|Relationship|List[int|Relationship]` ➡ relationships to be modified
+- `keys: List[string]` ➡ list of property names to be removed from the given relationships
+
+#### Output:
+
+- `relationship: Relationship` ➡ modified relationship(s)
+
+#### Usage:
+
+```cypher
+CREATE (matija:Person {name: "Matija"})
+CREATE (ivan:Person {name: "Ivan"})
+CREATE (ivan)-[:Friend {since: 'forever and ever', until: 'forever'}]->(matija);
+
+MATCH (:Person)-[friends:Friend]->(:Person) CALL create.remove_rel_properties(friends, ["until"]) YIELD relationship return relationship;
+
+```
+
+```plaintext
++------------------------------------+
+| relationship                       |
++------------------------------------+
+| {                                  |
+|     "id": 0,                       |
+|     "start: 1,                     |
+|     "end": 0,                      |
+|     "label": "Friend",             |
+|     "properties": {                |
+|       "since": "forever and ever"  |
+|     },                             |
+|     "type": "relationship"         |
+| }                                  |
++------------------------------------+
+```